Key Takeaways

What Causes Mesothelioma?

Mesothelioma begins in mesothelial tissue. The pleura lines the chest cavity and covers the lungs, the peritoneum lines the abdomen and covers many abdominal organs, and the pericardium surrounds the heart. Mesothelioma can also arise, very rarely, in tissue surrounding a testicle. These anatomical distinctions are covered in detail in our guide to the types of mesothelioma. Cancer develops when mesothelial cells accumulate genetic damage that allows them to grow and divide abnormally. Asbestos fibers can remain in the body for many years and contribute to persistent inflammation and cellular damage. The exact biological steps through which an individual exposure leads to mesothelioma are complex and remain incompletely understood.

The International Agency for Research on Cancer (IARC)⁴, part of the World Health Organization, classifies all forms of asbestos as carcinogenic to humans, with sufficient evidence that it causes mesothelioma along with cancers of the lung, larynx, and ovary. This is the strongest classification IARC assigns and reflects decades of consistent epidemiological and laboratory evidence. Asbestos is, by a wide margin, the most well-established cause of mesothelioma identified to date.

Cause Versus Risk Factor

Medical sources are careful to distinguish two related but different ideas when discussing mesothelioma. Understanding the difference helps explain why exposure to asbestos does not mean a diagnosis is inevitable, and why some people diagnosed have no identified exposure at all. Cause: a factor supported by evidence as contributing to disease development. Asbestos exposure meets this standard for mesothelioma. It is the best-documented, most consistently evidenced contributor identified to date. Risk factor: a characteristic or exposure associated with a greater likelihood of disease, without making it inevitable. Intensity, duration, fiber type, and individual susceptibility all modify risk without determining any one person’s outcome.

This distinction is not personalized medical advice. It reflects how these terms are used in the medical literature, not a calculation of any individual’s personal risk.

Asbestos Exposure

Asbestos is a group of naturally occurring fibrous minerals once widely used for insulation, fireproofing, and construction materials because of its heat resistance and durability. Exposure happens when asbestos-containing material is disturbed (cut, drilled, sanded, or broken down by age), releasing microscopic fibers into the air. The main recognized route of harmful exposure is inhalation of airborne asbestos fibers. Fibers may remain in the lungs or surrounding tissues for many years.

Exposure generally falls into a few categories. Occupational exposure occurs on the job, historically common in construction, shipbuilding, insulation work, manufacturing, and the military. Household or secondary exposure happens when a worker unknowingly carries fibers home on clothing, hair, or skin, exposing family members who never worked with asbestos directly. Environmental exposure can occur near naturally occurring asbestos deposits or in communities near asbestos-related industry. Older buildings, particularly those constructed before major local restrictions on asbestos use, may contain asbestos-containing materials. Some later products may also contain asbestos, depending on the country, product type, and applicable regulations. These materials are most likely to release fibers when they are damaged, deteriorating, or disturbed during renovation or demolition.

Many people diagnosed with mesothelioma do not immediately recall an asbestos exposure. This is common: exposure may have happened decades earlier, through a job held briefly, secondhand contact with a family member’s work clothes, or a renovation project, none of which may have seemed significant at the time. A gap in memory does not mean exposure didn’t happen. Importantly, having been exposed does not mean a person is certain to develop mesothelioma. For more on identifying and managing asbestos risk, see our guide to asbestos exposure.

Factors That Influence Asbestos-Related Risk

Not all asbestos exposure carries the same level of risk. Several factors appear to influence the likelihood that exposure will eventually contribute to disease, according to the National Cancer Institute²:

No level of asbestos exposure has been established as entirely risk-free, and no one can calculate an individual’s personal risk from these factors alone. They help explain population-level patterns rather than predict outcomes for a specific person.

Occupational and Household Exposure

Historically, occupational exposure has been the most commonly documented pathway to mesothelioma. Industries and roles with elevated historical exposure include shipbuilding and ship repair, construction and demolition, insulation installation, power plant and industrial maintenance, automotive brake and clutch work, and military service, particularly aboard older naval vessels. Regulations enacted since the 1970s have substantially reduced (though not eliminated) asbestos use and workplace exposure in many countries.

Household exposure is a recognized risk factor as well. Family members of asbestos workers, particularly those who laundered work clothing, could be exposed to fibers carried home. This pathway means that a person with no direct occupational history may still have a relevant exposure history worth discussing with a doctor.

Can Mesothelioma Occur Without Known Asbestos Exposure?

Yes. A subset of people diagnosed with mesothelioma have no documented or remembered asbestos exposure. This does not necessarily mean asbestos played no role (exposure earlier in life, especially secondary or environmental exposure, is not always recognized or recalled), but it also does not mean an undocumented exposure is the explanation in every case.

Researchers and clinicians consider other factors in these situations, including rare inherited genetic susceptibility and, less commonly, other environmental or occupational exposures. This remains an active area of clinical and scientific consideration rather than a fully settled question. This article cannot and does not attempt to determine the cause of any individual’s mesothelioma; that assessment belongs to a treating physician who can review a person’s complete medical, occupational, and family history.

BAP1 and Inherited Susceptibility

BAP1 tumor predisposition syndrome is a rare inherited condition caused by a germline (inherited, present in every cell) change in the BAP1 gene, which normally functions as a tumor suppressor. According to GeneReviews⁵, an expert-authored clinical genetics reference hosted by the National Center for Biotechnology Information, the syndrome is uncommon: population data suggest a heterozygous BAP1 pathogenic variant occurs in roughly 1 in nearly 27,000 people. People with this inherited change have an increased risk of several cancers, including mesothelioma, uveal melanoma, cutaneous melanoma, kidney cancer, and certain skin lesions.

It’s important to distinguish inherited (germline) BAP1 changes from a different, more common phenomenon: BAP1 changes that occur only within a tumor itself (somatic changes), which are not inherited and do not run in families. Somatic BAP1 changes are found in a substantial proportion of mesothelioma tumors generally, but this reflects changes that happened within the cancer cells themselves, not an inherited condition. Inherited germline BAP1 pathogenic variants account for only a small minority of mesothelioma cases. Published estimates suggest they are found in approximately 1% to 3% of isolated cases and about 6% to 8% of familial cases. These estimates vary between studies and should not be used to predict an individual patient’s risk.

A family history of mesothelioma or related cancers does not, by itself, confirm BAP1 tumor predisposition syndrome; only genetic testing can do that. A personal or family history, such as multiple relatives with mesothelioma, uveal melanoma, or related cancers, particularly at younger ages, can still help inform which additional genes are evaluated and how results are interpreted, but it is not a prerequisite for being offered testing in the first place. A positive germline result does not, by itself, prove why a particular person’s tumor developed; it identifies increased risk, not a confirmed individual cause. People considering testing can ask their doctor about a referral for genetic counseling before proceeding.

Does Asbestos Affect Every Mesothelioma Type the Same Way?

No. Asbestos is associated with mesothelioma at every anatomical site where the disease occurs, but the quantity and strength of the supporting evidence differ considerably by site. Our types of mesothelioma guide covers these anatomical distinctions in more detail.

Pleural. Pleural mesothelioma has by far the strongest and most established epidemiologic association with asbestos exposure, supported by decades of consistent occupational, laboratory, and population-level evidence.

Peritoneal. Asbestos exposure is also an established risk factor for peritoneal mesothelioma, though the epidemiologic patterns, such as typical exposure intensity and pathway, should not simply be assumed identical to pleural disease.

Pericardial. Evidence is far more limited for pericardial mesothelioma because primary disease at this site is exceptionally rare. A case-control study of rare-site mesothelioma reported an association between occupational asbestos exposure and pericardial disease¹⁰, but this limited registry-based evidence must not be presented as having the same strength as the pleural evidence base.

Tunica vaginalis. The evidence base is likewise small for mesothelioma of the tunica vaginalis, given how rare this tumor is. The same case-control study identified an association with occupational asbestos exposure at this site as well¹⁰, but association is not the same as proof of cause in any individual patient.

Other Possible or Uncommon Factors

A small number of other factors have a recognized, if more limited, evidence base connecting them to mesothelioma risk. These are far less common causes than asbestos and are included here for completeness, not because they represent a comparable level of risk.

What Does Not Appear to Cause Mesothelioma

It’s just as important to be clear about what current evidence does not support as a cause:

Why Mesothelioma Can Appear Decades Later

One of the most distinctive features of mesothelioma is its long latency period, meaning the time between the exposure that contributed to the disease and its diagnosis. Mesothelioma usually develops several decades after exposure, frequently after approximately 20 to 50 years, although shorter and longer intervals have been reported. The long delay reflects the gradual accumulation of inflammation, tissue injury, and cellular changes rather than an immediate response to exposure.

This latency period varies by individual and is not a fixed timeline that applies the same way to everyone. Someone exposed decades ago should not assume they are now “in the clear,” and someone more recently exposed should not expect symptoms to appear on a predictable schedule. This variability is one reason exposure history remains clinically relevant for many years after it occurred.

Can Mesothelioma Be Prevented?

There is no guaranteed way to prevent mesothelioma, but reducing avoidable asbestos exposure lowers preventable risk. A few general principles, consistent with occupational and environmental health guidance:

• Undisturbed asbestos-containing material in good condition is generally considered lower risk than material that is damaged, deteriorating, or being actively disturbed.
• Do not attempt to cut, sand, drill, remove, or otherwise disturb material you suspect contains asbestos yourself. Improper handling can release more fibers than leaving it alone.
• If asbestos is suspected in a home or workplace, a licensed asbestos abatement professional can assess and safely manage it according to local regulations.
• Following workplace safety regulations and using appropriate protective equipment where asbestos exposure is a known occupational risk reduces, but does not eliminate, exposure.

No medicine, supplement, or lifestyle intervention has been shown to eliminate mesothelioma risk after asbestos exposure. There is no universally recommended routine screening test for mesothelioma in asymptomatic people. People with substantial occupational, household, or environmental asbestos exposure should discuss individualized follow-up with a healthcare professional experienced in asbestos-related disease.

When to Speak With a Healthcare Professional

It’s reasonable to bring up mesothelioma risk with a doctor if any of the following apply: a known or suspected history of significant asbestos exposure, whether occupational, secondary, or environmental; persistent or unexplained symptoms such as chest pain, shortness of breath, or abdominal swelling that don’t have another clear explanation; or a family history suggestive of an inherited cancer syndrome, such as multiple relatives with mesothelioma or related cancers like uveal melanoma. A doctor can review your specific history and determine whether further evaluation, monitoring, or a genetics referral is appropriate.

If mesothelioma is diagnosed, our guides to symptoms, diagnosis, treatment, and prognosis explain what typically happens next.

Questions Patients May Ask

1. Does my work or residential history suggest possible asbestos exposure, even indirectly?
2. Should my exposure history be documented in my medical record?
3. Do my personal or family cancer patterns justify a referral for genetic counseling?
4. Should I be offered germline genetic testing, and what pretest counseling is available?
5. What symptoms, if any, should prompt further evaluation given my history?

Frequently Asked Questions

Sources and Medical References

1. National Cancer Institute. Mesothelioma, Causes and Risk Factors. 2025. View source.
2. National Cancer Institute. Asbestos Exposure and Cancer Risk. 2021. View source.
3. Agency for Toxic Substances and Disease Registry (ATSDR), U.S. CDC. Health Effects of Asbestos. 2024. View source.
4. International Agency for Research on Cancer (IARC). Asbestos, Overall Evaluations of Carcinogenicity. View source.
5. GeneReviews, NCBI Bookshelf. BAP1 Tumor Predisposition Syndrome. 2024. View source.
6. National Institute for Occupational Safety and Health (NIOSH), U.S. CDC. Erionite: An Emerging North American Hazard. 2011. View source.
7. Cancer Medicine. Relationship between exposure to ionizing radiation and mesothelioma risk: a systematic review and meta-analysis. 2022. doi:10.1002/cam4.4436.
8. Cancer Medicine. Radiation-induced mesothelioma among long-term solid cancer survivors: a longitudinal analysis of the SEER database. 2016. doi:10.1002/cam4.656.
9. Kindler HL, Ismaila N, Bazhenova L, et al. Treatment of Pleural Mesothelioma: ASCO Guideline Update. Journal of Clinical Oncology. 2025;43(8):1006–1038. doi:10.1200/JCO-24-02425.
10. Marinaccio A, Consonni D, Mensi C, et al. Association Between Asbestos Exposure and Pericardial and Tunica Vaginalis Testis Malignant Mesothelioma: A Case-Control Study and Epidemiological Remarks. Scandinavian Journal of Work, Environment & Health. 2020;46(6):609–617. doi:10.5271/sjweh.3895.

Mesothelioma Types at a Glance

What Are the Types of Mesothelioma?

Mesothelioma begins in mesothelial tissue, a thin lining that covers or surrounds several body cavities and organs. The anatomical name of the tumor is based on the site where it originated, not simply where disease is later found.

This distinction matters because cancer from another organ can spread to a serosal surface. For example, metastatic cancer involving the pleura or pericardium is not the same as primary pleural or pericardial mesothelioma. Determining the true site of origin relies on imaging, pathology, and the overall clinical context.

How Mesothelioma Is Classified

Mesothelioma is classified by anatomical site and histologic subtype. For example, a patient may have epithelioid pleural mesothelioma or biphasic pleural mesothelioma. The anatomical term describes the tumor’s origin, while the histologic term describes its microscopic appearance.

Classification by anatomical site

The four principal anatomical sites are pleural, peritoneal, pericardial, and tunica vaginalis. These sites differ in frequency, presentation, staging systems, surgical options, and available treatment evidence.

Classification by histology

Current pathology guidance recognizes three main histologic categories: epithelioid, biphasic, and sarcomatoid. Pathologists use morphology, immunohistochemistry, and, when necessary, molecular tests, rather than relying on a single marker.

Pleural Mesothelioma

Pleural mesothelioma develops in the pleura, the membrane surrounding the lungs and lining the chest cavity. It is by far the most common anatomical type, accounting for more than 8 in 10 mesotheliomas according to the American Cancer Society.

Symptoms usually reflect pleural and chest involvement rather than a unique mesothelioma pattern. Shortness of breath, chest pain, cough, fatigue, and pleural effusion may occur, but these symptoms are not specific to mesothelioma.

Pleural mesothelioma has the most developed evidence base among mesothelioma sites. It has a site-specific TNM staging system, and major randomized trials have evaluated systemic therapies specifically in unresectable pleural disease. In the United States, nivolumab plus ipilimumab is FDA-approved as first-line treatment for adults with unresectable pleural mesothelioma, while pembrolizumab with pemetrexed and platinum chemotherapy is FDA-approved as first-line treatment for unresectable advanced or metastatic pleural mesothelioma. These approvals should not be presented as automatically applying to peritoneal, pericardial, or tunica vaginalis mesothelioma.

Surgery may be considered for selected patients, typically after multidisciplinary review at experienced centers. Suitability for surgery depends on tumor extent, histology, cardiopulmonary fitness, treatment goals, and team expertise. Read our dedicated guide to pleural mesothelioma for more detail.

Peritoneal Mesothelioma

Peritoneal mesothelioma begins in the peritoneum, the membrane lining the abdominal cavity and covering many abdominal organs. It is the second most common anatomical type and accounts for most mesotheliomas arising outside the pleura.

Presentations may include abdominal swelling, pain or pressure, ascites, early satiety, bowel changes, fatigue, or unintended weight loss. These nonspecific findings typically require imaging and tissue diagnosis if mesothelioma is suspected.

Peritoneal disease should not be staged using the pleural AJCC Stage I–IV system. Specialists assess disease distribution, tumor burden, histology, resectability, patient fitness, and other clinical factors. Research staging systems exist but are not interchangeable with the pleural TNM framework.

For selected patients, cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) may be considered at experienced centers. Recent consensus highlights the need for individualized assessment and notes limited evidence on optimal systemic therapy timing. Clinical trial enrollment is encouraged when appropriate. Read our dedicated guide to peritoneal mesothelioma.

Pericardial Mesothelioma

Primary pericardial mesothelioma arises from the pericardium surrounding the heart. It is exceptionally uncommon, and the published evidence consists largely of case reports, small series, and retrospective reviews rather than randomized trials.

Patients may present with pericardial effusion, shortness of breath, chest discomfort, constrictive physiology, or cardiac tamponade. These findings are more often caused by other conditions, making diagnosis challenging. Imaging can detect pericardial abnormalities, but tissue sampling and expert pathology are often required.

There is no validated pericardial-specific AJCC Stage I–IV system. Clinicians instead evaluate the actual extent of pericardial involvement, invasion of cardiac or mediastinal structures, lymph-node or distant disease, and whether meaningful surgery is technically feasible.

No randomized trial has established a pericardial-specific treatment standard. Management may include urgent treatment of effusion or tamponade, surgery for selected patients, systemic therapy, radiation in certain cases, clinical trials, and supportive care. Evidence from pleural trials may inform specialist discussions but does not directly prove benefit in primary pericardial mesothelioma. Read our dedicated guide to pericardial mesothelioma.

Mesothelioma of the Tunica Vaginalis

Mesothelioma of the tunica vaginalis is a very rare tumor arising from the serosal lining around the testis. While “testicular mesothelioma” is common in patient materials, the anatomically precise term is mesothelioma of the tunica vaginalis, as it does not originate from testicular tissue itself.

Presentations may include hydrocele, scrotal swelling, a paratesticular mass, or findings initially mistaken for an inguinal hernia. Diagnosis is often unexpected and may only be confirmed after surgery and pathological examination.

Evidence is limited. A systematic review of published case-series data identified 275 patients and noted the absence of established treatment recommendations. Reported management has generally centered on surgery, with additional treatment individualized according to pathologic and clinical findings. Because the disease is so rare, treatment decisions are best discussed with specialists familiar with mesothelioma and genitourinary oncology.

Does Asbestos Affect All Mesothelioma Types in the Same Way?

No. The strength and quantity of evidence differ by anatomical site.

Asbestos exposure is the best-established environmental risk factor for pleural mesothelioma and is also associated with peritoneal mesothelioma. However, a recognized exposure history is not required for diagnosis, and exposure history alone is insufficient for diagnosis. Our asbestos exposure guide covers this topic in more detail.

Histologic Subtypes of Mesothelioma

Histology refers to the microscopic appearance of the tumor. It is distinct from anatomical site, though both influence treatment decisions and prognosis.

Epithelioid mesothelioma

Epithelioid is the most common histologic subtype. Tumors may display various morphologic patterns, and current guidance recommends grading epithelioid pleural mesothelioma using recognized histologic features. In general, epithelioid mesothelioma is associated with a more favorable prognosis than sarcomatoid mesothelioma, but histology is only one factor in prognosis.

Sarcomatoid mesothelioma

Sarcomatoid mesothelioma consists mainly of spindle-shaped malignant mesothelial cells. It is generally more aggressive and can be difficult to diagnose, as other spindle-cell tumors may appear similar.

Biphasic mesothelioma

Biphasic mesothelioma contains both epithelioid and sarcomatoid components. Adequate tissue sampling is essential, as limited biopsies may not capture the full tumor composition.

How pathology confirms mesothelioma

Pathologists do not diagnose mesothelioma from one immunohistochemical stain. Current consensus guidance recommends integrating morphology with a panel of markers that support mesothelial differentiation and markers that help exclude competing diagnoses.

Ancillary studies such as BAP1 or MTAP immunohistochemistry and CDKN2A deletion testing can be useful in selected settings, but their performance and interpretation depend on the anatomical site and diagnostic question.

How Symptoms Differ by Mesothelioma Type

Symptoms alone cannot determine the type of mesothelioma. Persistent or unexplained symptoms require medical evaluation, and the diagnostic approach depends on the affected site. Our symptoms guide covers this in more detail.

How Diagnosis Differs by Type

Diagnosis typically involves clinical history, imaging, and pathology, but the most effective tests vary by site. Pleural disease is evaluated with chest CT and thoracic procedures; peritoneal disease may require abdominal imaging and tissue sampling; pericardial disease often needs echocardiography and cardiac imaging; tunica vaginalis mesothelioma may be found during evaluation of a hydrocele or scrotal mass. Our diagnosis guide and imaging tests guide cover these approaches in more detail.

Fluid cytology may be helpful in certain cases, but its sensitivity varies by site and specimen. If mesothelioma is still suspected, adequate tissue sampling and expert pathology review are important. Imaging alone cannot determine histologic subtype. Our tests and biopsy guide covers these procedures in more detail.

How Staging Differs by Mesothelioma Type

Mesothelioma is not staged identically at every anatomical site.

Pleural mesothelioma has a dedicated TNM staging system developed through the International Association for the Study of Lung Cancer and incorporated into modern staging practice. The staging framework evaluates the primary pleural tumor, regional lymph nodes, and distant metastasis. Our mesothelioma stages guide covers this system in more detail.

Peritoneal, pericardial, and tunica vaginalis mesotheliomas do not have a widely validated AJCC Stage I–IV system like pleural mesothelioma. Clinicians use site-specific measures of disease extent, resectability, tumor burden, nodal or distant spread, and other prognostic factors.

How Treatment Differs by Mesothelioma Type

The key principle is that mesothelioma treatment is not a single universal approach. Anatomical site, histology, disease extent, symptoms, prior treatment, patient fitness, and care goals all influence treatment. Clinical trial eligibility may also differ by site, as some studies enroll only pleural mesothelioma. Our treatment guide covers the full range of approaches used across mesothelioma types.

How Prognosis Differs by Type

Prognosis varies widely and cannot be summarized with a single figure for all mesotheliomas. Anatomical site, histology, disease extent, treatment options, overall health, treatment era, and patient selection all affect outcomes.

Pleural mesothelioma has the largest trial and registry datasets. Peritoneal outcomes may differ significantly in selected patients at specialized centers, especially in surgical series. Pericardial and tunica vaginalis data are limited, making direct comparisons unreliable.

Our complete guide to Mesothelioma Prognosis and Survival covers these concepts in more detail.

Genetics and Germline Testing

Inherited cancer susceptibility affects a minority of patients with mesothelioma. Pathogenic germline variants can involve BAP1 and other cancer-predisposition genes; BAP1 is the best-characterized hereditary association in mesothelioma.

The 2025 ASCO pleural mesothelioma guideline states that all patients with mesothelioma should be offered germline testing. It also recommends that all patients who are offered testing be offered pretest genetic counseling with a qualified health professional. The genes evaluated may be informed by the patient’s personal and family history and other actionable cancer-risk genes.

Germline testing looks for inherited variants that can be present throughout the body, whereas somatic testing evaluates changes identified in tumor cells. Results should be interpreted with qualified genetic counseling.

Why Specialist Care Matters

Mesothelioma is uncommon, and pericardial and tunica vaginalis mesotheliomas are especially rare. Diagnosis and treatment may require collaboration among specialists in oncology, surgery, radiology, pathology, pulmonology, gastroenterology, cardiology, urology, genetics, and palliative care, depending on the anatomical site.

Specialist review is especially valuable when diagnosis is uncertain, major surgery is considered, disease arises outside the pleura, or clinical trial participation is possible.

Questions to Ask Your Medical Team

1. Where did my mesothelioma originate?
2. What histologic subtype was identified?
3. Has my pathology been reviewed by a pathologist experienced in mesothelioma?
4. Which staging or disease-extent system is appropriate for my anatomical type?
5. Which treatment evidence applies directly to my type of mesothelioma, and which recommendations are extrapolated from pleural disease?
6. Should my case be reviewed by a multidisciplinary mesothelioma team?
7. Should I be offered germline testing, and what pretest genetic counseling is available?
8. Are there clinical trials that accept patients with my specific anatomical type?

Frequently Asked Questions

References

1. American Cancer Society. Mesothelioma. Last revised February 3, 2026. Accessed August 2026.
2. Kindler HL, Ismaila N, Bazhenova L, et al. Treatment of Pleural Mesothelioma: ASCO Guideline Update. Journal of Clinical Oncology. 2025;43(8):1006–1038. doi:10.1200/JCO-24-02425.
3. Husain AN, Chapel DB, Attanoos R, et al. Guidelines for Pathologic Diagnosis of Mesothelioma: 2023 Update of the Consensus Statement From the International Mesothelioma Interest Group. Archives of Pathology & Laboratory Medicine. 2024;148(11):1251–1271. doi:10.5858/arpa.2023-0304-RA.
4. Wolf AS, Eisele M, Giroux DJ, et al. The International Association for the Study of Lung Cancer Pleural Mesothelioma Staging Project: Expanded Database to Inform Revisions in the Ninth Edition of the TNM Classification of Pleural Mesothelioma. Journal of Thoracic Oncology. 2024;19(8):1242–1252. doi:10.1016/j.jtho.2024.01.018.
5. Brown LM, Wilkins SG, Bansal VV, et al. Consensus Guideline for the Management of Peritoneal Mesothelioma. Annals of Surgical Oncology. 2026;33(6):5125–5141. doi:10.1245/s10434-025-17358-x.
6. McGehee E, Gerber DE, Reisch J, Dowell JE. Treatment and Outcomes of Primary Pericardial Mesothelioma: A Contemporary Review of 103 Published Cases. Clinical Lung Cancer. 2019;20(2):e152–e157. doi:10.1016/j.cllc.2018.11.008.
7. Marinaccio A, Consonni D, Mensi C, et al. Association Between Asbestos Exposure and Pericardial and Tunica Vaginalis Testis Malignant Mesothelioma: A Case-Control Study and Epidemiological Remarks. Scandinavian Journal of Work, Environment & Health. 2020;46(6):609–617. doi:10.5271/sjweh.3895.
8. Grogg JB, Fronzaroli JN, Oliveira P, et al. Clinicopathological Characteristics and Outcomes in Men With Mesothelioma of the Tunica Vaginalis Testis: Analysis of Published Case-Series Data. Journal of Cancer Research and Clinical Oncology. 2021;147(9):2671–2679. doi:10.1007/s00432-021-03533-6.
9. Baas P, Scherpereel A, Nowak AK, et al. First-line Nivolumab Plus Ipilimumab in Unresectable Malignant Pleural Mesothelioma (CheckMate 743): A Multicentre, Randomized, Open-label, Phase 3 Trial. The Lancet. 2021;397(10272):375–386. doi:10.1016/S0140-6736(20)32714-8.
10. Chu Q, Perrone F, Greillier L, et al. Pembrolizumab Plus Chemotherapy Versus Chemotherapy in Untreated Advanced Pleural Mesothelioma: A Phase 3 Randomized Controlled Trial. The Lancet. 2023;402(10419):2295–2306. doi:10.1016/S0140-6736(23)01613-6.
11. U.S. Food and Drug Administration. FDA Approves Pembrolizumab With Chemotherapy for Unresectable Advanced or Metastatic Malignant Pleural Mesothelioma. September 17, 2024.
12. National Cancer Institute. Nivolumab. Updated May 8, 2025. Accessed August 2026.

Pericardial Mesothelioma at a Glance

The rarity estimates and asbestos qualification are supported by systematic review and national registry evidence.

What Is Pericardial Mesothelioma?

The pericardium is a sac-like membrane surrounding the heart. Its layers are separated by a small amount of fluid that allows the heart to move normally as it beats.

Primary pericardial mesothelioma develops from mesothelial cells of this membrane.

The term primary is important. Cancers that begin elsewhere in the body can spread to the pericardium, and metastatic involvement of the pericardium is far more common than a cancer that originates there.

Primary pericardial mesothelioma may appear as a localized mass, but many reported tumors show diffuse involvement of the pericardium. Disease can also extend into nearby mediastinal structures, the myocardium, or major vessels.

Because this disease is exceptionally rare, many clinicians may never encounter a case in their careers.

How Rare Is Pericardial Mesothelioma?

Primary pericardial mesothelioma is among the rarest forms of mesothelioma.

A systematic review estimated that approximately 0.7% of mesotheliomas originate in the pericardium.

Population-level evidence also demonstrates how uncommon it is. The Italian National Mesothelioma Registry identified only 58 pericardial cases between 1993 and 2015, with annual standardized incidence rates of approximately 0.049 cases per million men and 0.023 cases per million women.

A contemporary review identified 103 published cases from 2000 through 2016, underscoring how limited the evidence base remains even when cases from many years and locations are combined.

A 2026 case report and literature review likewise describes primary pericardial mesothelioma as exceptionally rare, with diagnosis often difficult and disease-specific evidence still limited.

This rarity means treatment recommendations lack the volume and quality of evidence available for pleural mesothelioma or more common cancers.

What Causes Pericardial Mesothelioma?

The cause of primary pericardial mesothelioma remains incompletely understood.

Asbestos Exposure

The relationship between asbestos and primary pericardial mesothelioma is much less established than the relationship between asbestos and pleural mesothelioma.

Older case literature frequently failed to demonstrate a convincing exposure pattern. For example, one historical review identified recognized asbestos exposure in only 3 of 14 cases with available exposure information.

A 2020 national registry-based case-control study provides additional context; it supports an association with occupational asbestos exposure but does not by itself establish causation.

A case-control analysis based on the Italian National Mesothelioma Registry found that occupational asbestos exposure was associated with pericardial mesothelioma, with an odds ratio of 3.68 and a 95% confidence interval of 1.85–7.31. The study included only 58 pericardial cases because the disease itself is extremely rare.

A patient does not need a recognized history of asbestos exposure for clinicians to consider the diagnosis. Our asbestos exposure guide covers this topic more broadly across mesothelioma types.

Does Smoking Cause Pericardial Mesothelioma?

Smoking is not considered an established cause of mesothelioma.

While smoking is a significant risk factor for other cancers and cardiovascular diseases, it should not be used to determine the likelihood of pericardial mesothelioma.

Genetics and Germline Testing

Genetic susceptibility is increasingly recognized across mesothelioma, although evidence specifically characterizing inherited risk in primary pericardial mesothelioma is extremely limited.

Current ASCO guidance recommends that all patients with mesothelioma be offered germline testing. Patients offered germline testing should also be offered pretest genetic counseling with a qualified health professional.

Testing may include BAP1 and other genes associated with inherited cancer susceptibility.

For patients with pericardial mesothelioma, these findings should be interpreted cautiously. Most genetic recommendations are based on evidence from pleural and peritoneal disease, not large pericardial cohorts.

A germline result may have implications for the patient and relatives, but it does not explain why a pericardial tumor developed or determine a specific treatment.

Symptoms of Pericardial Mesothelioma

Symptoms are often caused by pericardial fluid accumulation, pressure around the heart, or impaired cardiac filling, rather than by features specific to mesothelioma.

Reported presentations include:

• shortness of breath
• chest pain or discomfort
• fatigue
• persistent cough
• palpitations
• reduced exercise tolerance
• swelling of the legs or abdomen
• recurrent pericardial effusion
• constrictive pericarditis
• cardiac tamponade

Chest discomfort and shortness of breath are among the most frequently reported symptoms in systematic reviews.

These symptoms have many more common causes. Infection, inflammatory disease, other forms of pericarditis, heart failure, and metastatic cancer can produce similar findings.

This lack of specificity often contributes to delayed diagnosis. Our symptoms guide covers the broader range of possible signs across all mesothelioma types.

Pericardial Effusion

A pericardial effusion is an abnormal accumulation of fluid within the pericardial space.

It is one of the most important presentations associated with primary pericardial mesothelioma.

Some patients experienced recurrent fluid accumulation after drainage, with tumor diagnosis made only after repeated investigations or surgery.

Pericardial effusion itself is not evidence of mesothelioma. Many other cardiovascular, inflammatory, infectious and malignant conditions can cause an effusion.

If fluid is recurrent or unexplained, especially when imaging shows pericardial thickening, nodules, or a mass, further investigation may be warranted.

What Is Cardiac Tamponade?

When pericardial fluid accumulates rapidly or creates enough pressure to interfere with cardiac filling, cardiac tamponade can develop.

Cardiac tamponade requires immediate medical attention.

The 2025 European Society of Cardiology guidelines define tamponade as a pericardial syndrome in which an effusion impairs diastolic filling and reduces cardiac output. Treatment centers on drainage of the pericardial fluid, generally by image-guided pericardiocentesis, and drainage should not be delayed in an unstable patient.

For patients with suspected cancer, initial management focuses on relieving hemodynamic effects and stabilizing the patient. Evaluation of the underlying cause, including malignancy, follows stabilization.

Pericardial mesothelioma is a possible malignant cause of tamponade, but it is exceptionally rare.

Constrictive Pericarditis

Pericardial mesothelioma can also lead to constrictive physiology.

When the pericardium becomes thickened, infiltrated, or rigid, normal filling of the heart can be impaired.

Patients may develop:

• fatigue
• breathlessness
• swelling
• reduced exercise tolerance
• or other signs resembling heart failure

Modern ESC guidance describes constriction as impaired cardiac filling caused by abnormal pericardial restriction, while published cases demonstrate that primary pericardial mesothelioma can occasionally be the underlying cause.

Many noncancerous conditions can cause constrictive pericarditis, so this finding alone does not confirm mesothelioma.

How Pericardial Mesothelioma Is Diagnosed

There is no single symptom, blood test, or imaging study that can establish a diagnosis of primary pericardial mesothelioma.

Diagnosis generally requires a combination of:

• clinical and cardiac assessment
• imaging
• evaluation for other possible primary cancers
• and pathology

Because metastatic cancer involving the pericardium is more common than primary pericardial mesothelioma, determining the true site of origin is essential in diagnosis. Our diagnosis guide covers this process in more detail.

Echocardiography

Echocardiography is often one of the first investigations performed when clinically important pericardial disease is suspected.

It can identify:

• pericardial effusion
• impaired cardiac filling
• signs of tamponade
• some pericardial masses
• and physiologic features of constriction

Echocardiography is valuable for assessing the impact of pericardial disease on heart function. ESC guidance recommends echocardiography as a primary tool for evaluating pericardial effusion and tamponade.

An echocardiogram cannot by itself establish that abnormal pericardial tissue is mesothelioma.

CT Imaging

Contrast-enhanced CT of the chest can provide detailed information about the anatomy of the pericardium and nearby structures.

Possible findings in published pericardial-mesothelioma cases include:

• pericardial thickening
• nodular pericardial disease
• pericardial masses
• effusion
• mediastinal involvement
• lymph-node abnormalities
• extension toward nearby cardiovascular structures

CT is also useful for evaluating the lungs, pleura, and mediastinum, and for identifying whether another primary cancer may be responsible for pericardial involvement.

Imaging cannot reliably determine histology.

Cardiac MRI

Cardiac MRI provides high soft-tissue contrast and may help specialists define the relationship between abnormal pericardial tissue and the heart or nearby structures.

It can be useful when evaluating:

• myocardial involvement
• major-vessel involvement
• pericardial thickening
• local mediastinal extension
• and constrictive physiology

Systematic-review data indicate that CT and MRI are more informative than plain radiography or echocardiography for defining tumor extent and involvement of adjacent structures. Our imaging tests guide covers CT, PET, and MRI in more detail.

Imaging strategies should be tailored to each patient.

PET/CT

PET/CT may be considered in selected patients to assess metabolically active disease and look for possible disease outside the immediate pericardial region.

Its role in primary pericardial mesothelioma has not been established through large prospective studies.

Increased metabolic activity is also not specific for mesothelioma and can occur with other cancers and inflammatory conditions.

Therefore, PET/CT does not replace the need for tissue diagnosis.

Pericardial Fluid Cytology

Fluid removed during pericardiocentesis is commonly sent for cytologic examination.

Cytology is an important diagnostic test for malignant pericardial effusions overall and can identify metastatic cancer involving the pericardium. In a 2025 multi-institutional study of 309 cases with concurrent cytology and pericardial biopsy, 99 were confirmed malignant; sensitivity was 84.8% for fluid cytology and 65.7% for biopsy. Most malignancies in that study were metastatic cancers rather than primary pericardial mesothelioma.

Primary pericardial mesothelioma poses a unique diagnostic challenge.

Older PPM-focused case literature identified malignant cells in only 4 of 17 examined pericardial-fluid specimens, and negative or inconclusive cytology has repeatedly been described before the eventual tissue diagnosis.

If imaging or clinical findings remain suspicious, further investigation and adequate tissue sampling may be necessary. Our tests and biopsy guide covers these procedures in more detail.

Pericardial Biopsy

Adequate tissue may be obtained through a pericardial biopsy, surgical pericardial window, pericardiectomy, or another procedure selected according to the patient’s anatomy and clinical condition.

Tissue provides architectural information needed to distinguish mesothelioma from reactive mesothelial proliferation and from other cancers involving the pericardium.

In some cases, diagnosis was only established after surgery for recurrent effusion or constrictive disease.

Because mesothelioma pathology is complex, specialist pathology review is recommended whenever possible.

How Pathologists Confirm Pericardial Mesothelioma

Mesothelioma should not be diagnosed based on one immunohistochemical marker.

The International Mesothelioma Interest Group recommends integrating morphology with an appropriate immunohistochemical panel and the clinical-radiologic context.

Markers supporting mesothelial differentiation can include:

• calretinin
• WT1
• D2-40
• cytokeratin 5/6

Markers expected to be negative in mesothelioma and useful for excluding carcinoma can include claudin-4, CEA, EpCAM, and TTF-1, selected according to the differential diagnosis. Mesothelioma diagnosis should rely on an appropriate panel rather than any single immunohistochemical marker.

Ancillary testing involving BAP1, MTAP, or CDKN2A may sometimes contribute to the assessment of mesothelial malignancy.

However, most evidence defining the performance of these tests comes from pleural and peritoneal mesothelioma rather than large cohorts of primary pericardial disease.

No individual biomarker should be used in isolation to diagnose primary pericardial mesothelioma.

Histologic Types

The broad histologic patterns recognized in mesothelioma at other serosal sites can also occur in the pericardium.

A modern 12-patient institutional cohort included nine epithelioid and three non-epithelioid tumors, but a cohort this small cannot define the true population distribution of histologic subtypes.

Histology should be considered as part of the overall clinical assessment, not as the sole basis for treatment decisions.

Conditions That Can Resemble Pericardial Mesothelioma

Many disorders are substantially more common than primary pericardial mesothelioma.

The differential diagnosis may include:

• metastatic carcinoma involving the pericardium
• lymphoma
• primary cardiac or mediastinal tumors
• inflammatory pericarditis
• infectious pericarditis
• reactive mesothelial proliferation
• other causes of recurrent pericardial effusion

Metastatic cancers, especially those from the lung and breast, account for most malignant pericardial effusions, far exceeding cases of primary pericardial mesothelioma.

Pathology should be interpreted alongside whole-body imaging and clinical history.

Is There a Staging System for Pericardial Mesothelioma?

There is no validated AJCC Stage I–IV system specifically established for primary pericardial mesothelioma.

The pleural mesothelioma staging system should not be applied to cancers originating in the pericardium.

Instead, specialists evaluate the actual distribution of disease.

Important considerations include:

• localized versus diffuse pericardial involvement
• myocardial invasion
• involvement of major cardiovascular structures
• mediastinal extension
• lymph-node disease
• distant metastases
• technical feasibility of meaningful surgical removal

In the contemporary 103-case review, metastatic or mediastinal spread was associated with worse survival.

These characteristics provide more clinical value than assigning an unsupported numerical stage.

Treatment of Pericardial Mesothelioma

There is no universally accepted standard treatment pathway for primary pericardial mesothelioma.

Treatment decisions therefore depend on factors such as:

• cardiovascular stability
• disease distribution
• histology
• surgical feasibility
• presence of metastatic disease
• symptoms
• previous therapy
• performance status
• overall health
• patient preferences

Most available evidence comes from published cases, retrospective reviews, and small institutional series.

Major treatment decisions should, whenever possible, involve a multidisciplinary team experienced in complex pericardial disease and mesothelioma. Our treatment guide covers the full range of approaches used across mesothelioma types.

Treating Pericardial Effusion and Tamponade

When a patient develops symptomatic pericardial effusion or cardiac tamponade, immediate management of the cardiovascular issue is the priority.

Image-guided pericardiocentesis may be used to drain fluid. Surgical drainage may be necessary if percutaneous drainage is not feasible or if another procedure is clinically preferable.

For recurrent effusions with hemodynamic consequences, a pericardial window may be considered in selected circumstances.

The appropriate strategy depends on:

• hemodynamic stability
• recurrence
• anatomy
• previous procedures
• overall cancer status
• expected disease course

For patients with suspected pericardial mesothelioma, drainage or surgical procedures may also provide an opportunity to obtain diagnostic tissue.

Surgery

The role of surgery depends largely on the tumor’s extent and location.

A localized, resectable tumor presents a very different clinical scenario than diffuse disease encasing the heart or invading major vessels.

Selected patients with localized disease have undergone substantial or complete resection, and prolonged survival has occasionally been reported.

However, complete resection is often not feasible due to diffuse pericardial involvement or invasion of critical structures.

Operations may therefore involve:

• tumor resection in highly selected cases
• partial or more extensive pericardiectomy
• debulking
• a pericardial window
• procedures primarily intended to relieve constriction or recurrent effusion

The 103-case contemporary review did not show a statistically significant survival advantage for surgery alone. This does not prove surgery is ineffective, as retrospective case series are strongly influenced by disease extent and patient selection.

Surgery should not be considered automatically appropriate solely based on a diagnosis of pericardial mesothelioma.

Multimodality Treatment

Due to common local progression and recurrence, combinations of surgery, chemotherapy, and radiation have been used in selected patients.

A Memorial Sloan Kettering retrospective cohort included only 12 patients with primary pericardial mesothelioma. Median overall survival for the cohort was 25.9 months. Three patients received trimodality therapy (surgery, chemotherapy, and radiation); their observed overall survival was 70.3 months versus 8.2 months among patients who did not receive trimodality therapy.

The cohort was very small, retrospective, and highly susceptible to selection bias. Patients who received surgery and multiple treatments likely had different disease characteristics and overall health compared to those with advanced, unresectable disease.

Therefore, the study does not establish that trimodality therapy provides the same benefit for all patients with primary pericardial mesothelioma.

Systemic Chemotherapy

No chemotherapy regimen has been validated specifically for primary pericardial mesothelioma in randomized clinical trials.

Most systemic treatment practices are extrapolated from mesothelioma at other sites and from pericardial case reports.

Platinum-based chemotherapy, commonly combined with pemetrexed, is among the most frequently reported systemic approaches.

In the 2000–2016 published-case review of 103 patients, median survival was reported as 13 months among patients who received chemotherapy versus 0.5 months among those who did not, and chemotherapy remained associated with improved survival in multivariable analysis.

This comparison requires substantial caution.

The study was not randomized. Patients receiving treatment were likely healthier, may have had different disease characteristics, and had to survive long enough to begin chemotherapy.

Therefore, the finding demonstrates an association, not proof that chemotherapy leads to a specific survival benefit for individual patients.

The oncology team should individualize systemic treatment decisions.

Immunotherapy

Immunotherapy has changed treatment for some pleural mesothelioma patients, but these results cannot be directly applied to primary pericardial mesothelioma.

No dedicated randomized trials have demonstrated a survival benefit from nivolumab plus ipilimumab, pembrolizumab, or other immune-checkpoint regimens specifically in primary pericardial mesothelioma.

Published evidence is largely limited to individual case reports.

A 2021 report described a patient with primary pericardial mesothelioma treated with an immune-checkpoint inhibitor as second-line treatment.

A separate 2024 case report described a multimodality approach involving pericardial surgery followed by carboplatin, pemetrexed and pembrolizumab and then radiation therapy.

Case reports demonstrate that treatments have been used and document individual outcomes, but they cannot establish a standard of care or predict responses in other patients.

Immunotherapy for primary pericardial mesothelioma should therefore be considered an individualized specialist decision, potentially informed by:

• evidence from other mesothelioma sites
• previous treatment
• histology and other tumor characteristics
• comorbidities
• expected toxicity
• clinical-trial availability

Radiation Therapy

Radiation therapy may have a role in selected circumstances, but its optimal use in primary pericardial mesothelioma is uncertain.

Potential uses may include:

• selected postoperative multimodality treatment
• local control of unresectable disease
• palliation of a specific symptomatic site

Radiation near the heart requires careful treatment planning because the heart, lungs, esophagus, and other surrounding structures can be sensitive to radiation.

Small retrospective series have reported prolonged survivors who received radiation as one component of multimodality therapy, but those observations cannot establish a universal treatment benefit.

What Happens if the Disease Cannot Be Removed?

Unresectable disease does not mean medical care stops.

Depending on the patient’s condition and goals, management may include:

• systemic therapy
• control of recurrent pericardial effusion
• treatment of cardiovascular symptoms
• radiation for selected local problems
• clinical trials
• supportive and palliative care

Treatment goals may also change over time according to response, progression and the patient’s cardiovascular and general health.

Recurrent Pericardial Effusion

Repeated fluid accumulation can substantially affect symptoms and quality of life.

Management depends on:

• how rapidly the fluid returns
• whether cardiac filling is affected
• symptoms
• previous drainage procedures
• disease status
• overall health

Some patients may undergo additional pericardiocentesis, while others may be considered for a pericardial window or another surgical approach intended to provide more durable drainage.

ESC guidance specifically recognizes pericardial-window procedures as an option for relapsing effusion with hemodynamic compromise despite conservative management or previous percutaneous drainage.

There is no single procedure appropriate for every patient.

Supportive and Palliative Care

Supportive care should be integrated throughout treatment.

Symptoms that may require active management include:

• shortness of breath
• chest discomfort
• fatigue
• reduced appetite
• sleep disturbance
• anxiety
• limitations in daily activity

Palliative care is not synonymous with hospice or stopping cancer treatment.

Palliative-care specialists can work alongside cardiology, oncology and surgery to help manage symptoms, support decision-making and protect quality of life while anticancer treatment continues.

Clinical Trials

Clinical research is especially important for primary pericardial mesothelioma because disease-specific treatment evidence is extremely limited.

There are too few patients for most therapeutic questions to have been answered through dedicated randomized trials.

Depending on the clinical situation, specialists may investigate trials involving:

• mesothelioma
• rare cancers
• immunotherapy
• molecularly selected cancers
• novel systemic treatments

Eligibility depends on the individual protocol and must be determined by the clinical-trial team.

Evidence generated in a trial restricted to pleural mesothelioma should not automatically be presented as proof of efficacy in pericardial disease.

Pericardial Mesothelioma Prognosis

Primary pericardial mesothelioma is generally an aggressive disease, but survival statistics require careful interpretation.

In the 103-case review of reports published from 2000 through 2016, median overall survival was approximately 6 months. Metastatic or mediastinal spread was associated with worse survival. This is a historical published-case estimate, not a contemporary population-based survival estimate.

These numbers should not be interpreted as a fixed life expectancy.

The published-case literature combines patients:

• treated in different eras
• diagnosed at different stages of disease
• receiving very different treatments
• with different levels of cardiovascular compromise
• and with different possibilities for surgery

Selected contemporary patients have experienced substantially longer survival.

For example, the 12-patient Memorial Sloan Kettering cohort reported median overall survival of 25.9 months. Still, its small size and strong potential for patient-selection bias make direct comparison with historical case reviews inappropriate.

Factors That May Affect Prognosis

Potential prognostic considerations include:

• extent of pericardial disease
• mediastinal involvement
• distant metastases
• involvement of critical cardiovascular structures
• feasibility of meaningful resection
• histology
• cardiovascular health
• general performance status
• ability to receive systemic or multimodality treatment

Pericardial-specific evidence is strongest for disease extent; the independent prognostic effects of histology and treatment selection remain uncertain because available cohorts are very small and retrospective. In the 103-case review, mediastinal or metastatic spread was associated with worse survival, while chemotherapy was associated with longer survival in retrospective analysis.

Because primary pericardial mesothelioma is so rare, the evidence supporting individual prognostic factors is considerably weaker than it is for pleural mesothelioma. Our complete guide to Mesothelioma Prognosis and Survival covers these concepts in more detail.

No online calculator can reliably predict an individual patient’s prognosis.

Why Specialist Care Matters

Primary pericardial mesothelioma sits at the intersection of oncology and cardiovascular medicine.

A multidisciplinary team may include:

• cardiology
• cardio-oncology
• cardiac or thoracic surgery
• medical oncology
• radiation oncology
• cardiac imaging
• pathology
• genetics
• palliative care

Important specialist questions include:

• Did the tumor truly originate in the pericardium?
• Has the pathology been confirmed?
• Is the tumor localized or diffuse?
• Is the myocardium involved?
• Are major vessels involved?
• Is there mediastinal or distant disease?
• Is meaningful surgical removal feasible?
• How should recurrent pericardial fluid be managed?
• Is systemic therapy appropriate?
• Is there a realistic role for radiation?
• Is a clinical trial available?

Because the disease is exceptionally rare, a second opinion can be particularly valuable before major surgery or when the diagnosis remains uncertain. Obtaining a second opinion does not require transferring all future care to another hospital. A specialist center can review pathology, imaging, and treatment plans while some care continues locally.

Questions to Ask Your Medical Team

1. Has my diagnosis been reviewed by a pathologist experienced in mesothelioma?
2. Are you confident that the cancer originated in the pericardium rather than spreading there from another site?
3. What histologic subtype do I have?
4. Is the tumor localized or diffuse?
5. Does imaging show involvement of the myocardium, coronary vessels, or major vessels?
6. Is there mediastinal, lymph-node, or distant disease?
7. Do I have a clinically important pericardial effusion?
8. Is the effusion affecting how my heart fills or pumps?
9. What is the best strategy for managing recurrent fluid?
10. Is meaningful surgical removal possible?
11. What would surgery be intended to achieve in my case?
12. Should platinum-pemetrexed chemotherapy be considered?
13. How much evidence supports the proposed systemic treatment specifically for pericardial mesothelioma?
14. Is immunotherapy reasonable in my situation, and how much of the evidence is extrapolated from pleural mesothelioma?
15. Could radiation therapy have a role?
16. Should I have germline genetic testing and genetic counseling?
17. Are there clinical trials for which I might be eligible?
18. Would review at a center experienced in both mesothelioma and complex pericardial disease be useful?

Frequently Asked Questions

References

1. McGehee E, Gerber DE, Reisch J, Dowell JE. Treatment and Outcomes of Primary Pericardial Mesothelioma: A Contemporary Review of 103 Published Cases. Clinical Lung Cancer. 2019;20(2):e152–e157. doi:10.1016/j.cllc.2018.11.008.
2. Cao S, Jin S, Cao J, et al. Malignant Pericardial Mesothelioma: A Systematic Review of Current Practice. Herz. 2018;43(1):61–68. doi:10.1007/s00059-016-4522-5.
3. Marinaccio A, Consonni D, Mensi C, et al. Association Between Asbestos Exposure and Pericardial and Tunica Vaginalis Testis Malignant Mesothelioma: A Case-Control Study and Epidemiological Remarks. Scandinavian Journal of Work, Environment & Health. 2020;46(6):609–617. doi:10.5271/sjweh.3895.
4. Alves de Lima A, Carrero MC, Stutzbach PG, et al. Primary Pericardial Mesothelioma: A Rare and Aggressive Malignancy — Case Report and Literature Review. American Journal of Cardiology. 2026;263:22–26. doi:10.1016/j.amjcard.2025.12.008.
5. Nilsson A, Rasmuson T. Primary Pericardial Mesothelioma: Report of a Patient and Literature Review. Case Reports in Oncology. 2009;2(2):125–132. doi:10.1159/000228894.
6. Offin M, De Silva DL, Sauter JL, et al. Multimodality Therapy in Patients With Primary Pericardial Mesothelioma. Journal of Thoracic Oncology. 2022;17(12):1428–1432. doi:10.1016/j.jtho.2022.08.017.
7. Kindler HL, Ismaila N, Bazhenova L, et al. Treatment of Pleural Mesothelioma: ASCO Guideline Update. Journal of Clinical Oncology. 2025;43(8):1006–1038. doi:10.1200/JCO-24-02425. Although the guideline’s target population is pleural mesothelioma, Recommendations 7.1 and 7.6 explicitly address all patients with mesothelioma for germline testing and pretest counseling.
8. Husain AN, Chapel DB, Attanoos R, et al. Guidelines for Pathologic Diagnosis of Mesothelioma: 2023 Update of the Consensus Statement From the International Mesothelioma Interest Group. Archives of Pathology & Laboratory Medicine. 2024;148(11):1251–1271. doi:10.5858/arpa.2023-0304-RA.
9. Schulz-Menger J, Collini V, Gröschel J, et al. 2025 ESC Guidelines for the Management of Myocarditis and Pericarditis. European Heart Journal. 2025;46(40):3952–4041. doi:10.1093/eurheartj/ehaf192.
10. Takeda K, Gereg C, Liu X, et al. Higher Sensitivity of Pericardial Fluid Cytology Than Biopsy in Malignant Effusions With Potential Explanation of False-Negative Cytology: A Multi-Institutional Analysis. Cytopathology. 2025;36(1):31–40. doi:10.1111/cyt.13447.
11. Arponen O, Salo V, Lönnberg A, et al. Primary Pericardial Mesothelioma: A Case Report of a Patient Treated With an Immune Checkpoint Inhibitor as the Second-Line Treatment. Acta Oncologica. 2021;60(5):687–691. doi:10.1080/0284186X.2021.1887515.
12. Gong J, Wu X, Wang J. A Case of Primary Pericardial Mesothelioma Treated With Multimodal Combined Therapy. Frontiers in Cardiovascular Medicine. 2024;11:1433668. doi:10.3389/fcvm.2024.1433668.

Pleural Mesothelioma at a Glance

What Is Pleural Mesothelioma?

The pleura is made up of two thin layers of tissue. The visceral pleura covers the lungs, and the parietal pleura lines the inside of the chest wall. A small amount of fluid between these layers helps them move smoothly as you breathe.

Pleural mesothelioma starts when cells in this lining become cancerous. Unlike most lung cancers, it does not start inside the lung. Instead, it usually spreads along the pleura and can eventually affect nearby areas like the chest wall, diaphragm, mediastinum, or pericardium.

Because of these differences, pleural mesothelioma is not the same as lung cancer. They have different biology, staging, and treatment approaches.

The term diffuse pleural mesothelioma is often used in modern pathology and staging literature because the cancer commonly grows across broad areas of the pleura rather than forming one clearly defined mass.

How Common Is Pleural Mesothelioma?

Mesothelioma is rare compared with cancers such as lung, breast, prostate or colorectal cancer. Pleural mesothelioma accounts for the large majority of mesothelioma diagnoses.

Because pleural mesothelioma is rare, diagnosis and treatment may benefit from clinicians and centers with specific experience managing the disease.

This is why getting a second opinion from a center that specializes in pleural mesothelioma can be helpful, especially when making big treatment decisions like surgery or systemic therapy.

What Causes Pleural Mesothelioma?

Asbestos exposure

Asbestos exposure is the major established risk factor for pleural mesothelioma.

Asbestos is a group of naturally occurring mineral fibers that were widely used in insulation, construction materials, shipbuilding, and many industrial products because of their resistance to heat and fire.

When materials with asbestos are disturbed, tiny fibers can get into the air and be breathed in. Some inhaled asbestos fibers can remain in the body for many years and contribute to biological changes associated with the development of mesothelioma.

Mesothelioma often appears decades after the original exposure.

Workplace exposure has been a major risk, especially in jobs where people handled asbestos materials. Exposure can also happen outside of work, such as from the environment or from asbestos fibers brought home on clothing in the past.

Not everyone who is exposed to asbestos will get mesothelioma, and some people with the disease do not recall any specific exposure. Our asbestos exposure guide covers this topic in more detail.

Does smoking cause mesothelioma?

Smoking is not considered an established cause of pleural mesothelioma.

However, smoking is a major cause of lung cancer. People who have been exposed to asbestos and also smoke have a much higher risk of getting lung cancer, which is different from mesothelioma.

Other risk factors

Researchers have studied additional factors that might contribute to mesothelioma in a minority of cases.

Inherited changes involving the BAP1 gene can predispose some families to mesothelioma and several other tumors. Therapeutic radiation and certain unusual mineral exposures have also been investigated.

These rare situations do not change the main fact: asbestos is still the main known environmental cause of pleural mesothelioma.

Symptoms of Pleural Mesothelioma

Symptoms usually appear slowly and are not unique to mesothelioma. They can be caused by the tumor, inflammation of the pleura, or fluid building up around the lung.

Common presentations include shortness of breath, persistent chest discomfort or pain, pleural effusion, persistent cough, fatigue, reduced appetite, and unintended weight loss.

Some people initially notice only increasing breathlessness. Others are evaluated after imaging performed for another reason shows pleural fluid or abnormal pleural thickening.

These symptoms are much more often caused by other conditions, not mesothelioma. Having these symptoms does not mean you have mesothelioma.

If you have ongoing or unexplained breathing problems, you should see a healthcare professional, especially if you have a history of asbestos exposure. Our symptoms guide covers the broader range of possible signs across all mesothelioma types.

How Pleural Mesothelioma Is Diagnosed

Diagnosing pleural mesothelioma usually takes several steps, not just one test. Our diagnosis guide covers this process in more detail.

Medical history and examination

The evaluation typically begins with symptoms, general medical history, and possible occupational or environmental asbestos exposure.

An exposure history can support clinical suspicion, but the absence of a known asbestos exposure does not exclude mesothelioma.

Imaging

A chest X-ray may reveal pleural fluid or other abnormalities, but computed tomography (CT) generally provides much more detail.

CT can help identify pleural thickening, nodularity, pleural effusion, and involvement of nearby structures. It is also important for clinical staging.

PET/CT may be useful in selected patients when clinicians are assessing disease extent or looking for possible metastatic disease. MRI can provide additional information in certain situations, particularly when detailed evaluation of invasion into nearby structures is needed. Our imaging tests guide covers CT, PET, and MRI in more detail.

Imaging tests can make doctors more or less suspicious of mesothelioma, but these tests alone usually cannot confirm the diagnosis.

Pleural fluid testing

Many patients develop a pleural effusion, which is an abnormal collection of fluid between the pleural layers.

Thoracentesis can remove some of this fluid. The procedure can help relieve breathlessness and provides fluid that can be examined for malignant cells.

However, testing pleural fluid has important limits for diagnosing mesothelioma. A negative result does not rule out the disease, and the test may not give enough information to plan treatment.

Biopsy

When planning treatment, it is usually important to get enough tissue for testing.

Depending on the clinical situation, tissue may be obtained through thoracoscopy or an image-guided pleural biopsy.

Thoracoscopy lets doctors look inside the pleural cavity and take several tissue samples. The type of biopsy depends on imaging results, the patient’s health, risks of the procedure, and the planned treatment. Our tests and biopsy guide covers these procedures in more detail.

How pathologists confirm pleural mesothelioma

Diagnosing mesothelioma can be hard because other cancers can spread to the pleura and look similar under the microscope.

A pathologist evaluates the tissue architecture and uses a panel of immunohistochemical markers to distinguish mesothelioma from metastatic carcinoma and other tumors.

No single conventional immunohistochemical marker is sufficient in every case.

Modern pathology may also use tests involving BAP1, MTAP and CDKN2A when distinguishing malignant mesothelioma from benign mesothelial proliferations is difficult. For example, loss of BAP1 or MTAP expression or homozygous deletion of CDKN2A can provide evidence supporting malignancy in the appropriate pathological setting.

Doctors must look at these test results as part of the whole pathology review, not use them alone to diagnose cancer.

Because diagnosing mesothelioma can be tricky, having an expert in thoracic pathology review the case is especially helpful when the diagnosis or type is unclear.

Genetic counseling and germline testing

The 2025 ASCO guideline recommends offering germline genetic testing to all patients with mesothelioma. Testing looks for inherited pathogenic variants that can contribute to cancer susceptibility, including changes involving BAP1 and other cancer-risk genes.

A positive result does not mean that asbestos exposure was unimportant, and it does not by itself determine treatment. However, it may provide information relevant to prognosis, additional cancer surveillance and the potential cancer risk of biological relatives. Genetic testing should ideally be accompanied by counseling from a qualified professional so patients understand the medical and potential family implications of the results.

Histologic Types of Pleural Mesothelioma

Pleural mesothelioma is divided into three major histologic categories.

The type of mesothelioma seen under the microscope (histology) is important because it can affect prognosis and treatment choices.

However, histology is just one factor. Stage, lymph node involvement, overall health, treatment options, and tumor biology also affect outcomes.

Pleural Mesothelioma Staging: AJCC/IASLC Version 9

Pleural mesothelioma is currently staged using the TNM Version 9 system developed from the International Association for the Study of Lung Cancer staging project and incorporated into modern AJCC staging.

TNM describes three different aspects of the disease.

T describes the extent of the primary pleural tumor.
N describes involvement of regional lymph nodes.
M describes distant metastatic spread.

Version 9 introduced important changes to clinical assessment of the primary tumor. In addition to invasion of surrounding structures, radiologic measurements of pleural tumor thickness now contribute to clinical T classification.

So, information from older articles using previous TNM versions may not apply to patients staged with Version 9.

Stage I

Stage I corresponds to T1 N0 M0 disease.

The tumor remains relatively limited by Version 9 criteria, with no regional lymph-node involvement and no distant metastasis.

Stage II

Stage II includes T2 N0 M0 and T1 N1 M0 disease.

The cancer may therefore have greater local pleural involvement without lymph-node spread, or relatively limited primary disease with involvement of certain ipsilateral regional lymph nodes.

Stage IIIA

Stage IIIA includes T1 N2 M0, T2 N1–N2 M0, and T3 with any N category, M0.

This group includes many different situations, so treatment decisions should not be made based only on the stage label.

Stage IIIB

Stage IIIB corresponds to T4, any N, M0.

T4 disease involves extensive invasion into structures that generally makes complete macroscopic surgical removal unrealistic.

Stage IV

Stage IV is defined by M1 distant metastatic disease, regardless of T or N category.

Examples can include spread to distant organs or other distant anatomical sites. Our complete mesothelioma stages guide covers each stage individually, including dedicated guides to Stage 1, Stage 2, Stage 3, and Stage 4 mesothelioma.

Treatment of Pleural Mesothelioma

There is no one-size-fits-all treatment plan for pleural mesothelioma.

Treatment choices depend on many factors, such as stage, type of mesothelioma, whether surgery is possible, symptoms, overall health, past treatments, patient preferences, and available clinical trials.

Today, treatment often includes systemic therapy.

For some patients, surgery or radiation may also be part of a broader treatment plan. Our treatment guide covers the full range of approaches used across all stages.

Immunotherapy with nivolumab and ipilimumab

Nivolumab and ipilimumab are immune-checkpoint inhibitors that target different mechanisms used by cancer cells to suppress immune responses.

The phase III CheckMate 743 trial compared first-line nivolumab plus ipilimumab with platinum-pemetrexed chemotherapy in previously untreated patients with unresectable pleural mesothelioma.

The original analysis demonstrated longer overall survival with nivolumab plus ipilimumab. Long-term follow-up has since strengthened the evidence that a subset of patients can experience durable benefit.

In the 2026 five-year analysis, overall survival at five years was 14% with nivolumab plus ipilimumab compared with 6% with chemotherapy in the trial population.

These are group-level survival estimates, not predictions for an individual patient. A person’s outlook depends on many additional clinical factors.

The FDA has approved nivolumab plus ipilimumab as first-line treatment for adults with unresectable malignant pleural mesothelioma.

Immune-checkpoint inhibitors can cause inflammatory side effects when activated immune cells affect healthy organs. Treatment therefore requires monitoring by clinicians experienced with immunotherapy.

Pembrolizumab with platinum and pemetrexed

Another first-line strategy combines immunotherapy with chemotherapy.

The phase III KEYNOTE-483 trial studied pembrolizumab added to platinum-pemetrexed chemotherapy in previously untreated advanced pleural mesothelioma.

Median overall survival in the study was 17.3 months with pembrolizumab plus chemotherapy versus 16.1 months with chemotherapy alone. The objective response rate was 52% versus 29%.

In September 2024, the U.S. Food and Drug Administration approved pembrolizumab with pemetrexed and platinum chemotherapy as first-line treatment for adults with unresectable advanced or metastatic malignant pleural mesothelioma.

Again, the median survival from a clinical trial is not the same as an individual’s expected lifespan. Some people live less time, while others live much longer.

Chemotherapy

Platinum-based chemotherapy remains an important part of pleural mesothelioma treatment.

The traditional backbone consists of pemetrexed combined with a platinum drug, usually cisplatin or, in appropriate circumstances, carboplatin.

Chemotherapy can reduce tumor burden or slow disease progression in some patients. It may be given alone or as part of an immunotherapy-containing regimen, depending on the clinical situation.

Choosing the best first treatment is not just about which trial showed the longest survival. The type of mesothelioma, other health problems, side effects, kidney function, and patient preferences all play a role.

This is why the oncology team should tailor treatment to each patient.

What Is the Role of Surgery?

Whether major surgery should be used to remove as much tumor as possible in pleural mesothelioma is now one of the most debated topics in treatment.

Historically, surgical strategies have included pleurectomy/decortication (P/D), extended pleurectomy/decortication (eP/D), and extrapleural pneumonectomy (EPP).

Pleurectomy/decortication removes pleural tumor while preserving the lung. Extended P/D may additionally remove involved portions of structures such as the diaphragm or pericardium when necessary.

Extrapleural pneumonectomy is a bigger operation that removes the affected lung, pleura, and other involved tissues. This surgery is now used much less often.

Why the evidence changed

Historically, much of the evidence supporting aggressive surgery came from highly selected patients treated at specialist centers rather than randomized trials.

The phase III MARS 2 randomized trial provided important new evidence. In patients considered to have resectable disease, adding extended pleurectomy/decortication to chemotherapy was associated with worse survival during the study period and more serious adverse events compared with chemotherapy alone.

These results have changed how doctors talk about surgery for pleural mesothelioma.

Current ASCO guidance does not recommend surgical cytoreduction solely because a tumor appears anatomically resectable. Surgery may still be considered for highly selected patients with favorable features, particularly clinically early-stage T1–3 N0 epithelioid disease, after comprehensive staging and multidisciplinary review at an experienced center.

When surgery is considered, lung-sparing approaches are generally preferred over extrapleural pneumonectomy.

If you are thinking about major surgery, it is best to have your case reviewed at a center with experience in pleural mesothelioma. There, you can discuss the benefits, risks, and other options in detail.

Radiation therapy

Radiation therapy can be used in different ways for pleural mesothelioma, but whether it is used depends a lot on each person’s situation.

It may be considered to relieve localized pain or other symptoms caused by tumor growth. In selected specialist-center treatment strategies, radiation may also form part of multimodality management.

Treating the whole pleural surface with radiation is difficult because important organs like the remaining lung, heart, spinal cord, and liver are close by.

Modern techniques allow radiation oncologists to target treatment more precisely, but radiation therapy is not generally used as a standalone curative treatment for pleural mesothelioma.

Managing pleural effusion and other symptoms

Treatments aimed at the cancer and those aimed at symptoms work together and are not in competition.

Pleural effusion can compress the lung and contribute substantially to breathlessness.

Thoracentesis can temporarily remove fluid from the pleura. If the fluid keeps coming back, doctors may suggest options like a permanent catheter or pleurodesis, depending on your symptoms, lung function, overall health, and preferences.

Other supportive treatments can help with pain, breathlessness, tiredness, appetite, movement, sleep, and emotional or practical issues.

Palliative care does not mean stopping cancer treatment.

Palliative care focuses on managing symptoms, improving quality of life, and supporting patients and families.

It can be started while you are still getting active cancer treatment.

Palliative care and hospice are not the same. Hospice is for a different stage and goal of care, while palliative care can be helpful much earlier during cancer treatment.

Clinical trials

Clinical trials are especially important for rare cancers like pleural mesothelioma.

Researchers are investigating new immune-based strategies, treatment combinations, targeted approaches, cellular therapies, biomarkers and different ways of sequencing existing treatments.

A trial’s eligibility requirements may depend on previous therapy, histology, stage, tumor biomarkers, organ function, performance status and many other factors.

A website cannot tell if a specific patient qualifies for a clinical trial.

If you are interested in joining a research study, talk to your oncology team and check official registries like ClinicalTrials.gov.

Pleural Mesothelioma Prognosis

The outlook for pleural mesothelioma can be very different from one person to another.

Important factors can include stage, histologic subtype, lymph-node involvement, performance status, overall health, age, tumor burden, resectability, and response to treatment.

Epithelioid mesothelioma usually has a better outlook than sarcomatoid or biphasic types, but the type alone cannot predict what will happen to each person.

Current population survival statistics

The American Cancer Society currently reports U.S. SEER five-year relative survival estimates for people diagnosed with pleural mesothelioma from 2015 through 2021:

These figures require careful interpretation.

SEER localized, regional, and distant categories are not the same as AJCC Stage I, II, III, and IV.

These statistics are based on people treated in the past. Since treatments have changed with new immunotherapy and chemoimmunotherapy, older survival data may not show what happens to patients diagnosed today.

Most importantly, survival statistics are about groups of people and cannot predict how long any one person will live.

For a deeper explanation, see our complete guide to Mesothelioma Prognosis and Survival.

Why specialist care can matter

Pleural mesothelioma involves several different medical specialties.

An experienced multidisciplinary team may include medical oncology, thoracic surgery, radiation oncology, pulmonology, thoracic radiology, pathology, interventional pulmonology and palliative-care specialists.

Specialist evaluation can be particularly valuable for confirming pathology, interpreting Version 9 staging, determining whether surgery deserves consideration, selecting systemic treatment, managing recurrent pleural effusion and identifying appropriate clinical trials.

Getting a second opinion does not mean you have to switch all your care to another hospital. Sometimes, a specialist center can review your case while you continue most of your treatment closer to home.

Questions to Ask Your Medical Team

1. Has my diagnosis been reviewed by a pathologist experienced in pleural mesothelioma?
2. What histologic subtype do I have?
3. What is my TNM Version 9 stage?
4. Has the cancer spread to regional lymph nodes or distant organs?
5. Is my disease considered resectable or unresectable, and what factors led to that conclusion?
6. What is the main goal of treatment in my situation?
7. Which first-line systemic treatment options are reasonable to discuss?
8. What potential benefits and side effects are most relevant to me?
9. If surgery is being considered, how does current evidence such as MARS 2 apply to my case?
10. Would review at a multidisciplinary mesothelioma center be useful?
11. Are there clinical trials that fit my diagnosis and previous treatment?
12. What can be done now to manage breathlessness, pleural effusion, pain, or other symptoms?

Frequently Asked Questions

References

1. National Cancer Institute. Mesothelioma. NCI Cancer Types. Current online clinical resource.
2. National Cancer Institute. Asbestos Exposure and Cancer Risk Fact Sheet. National Cancer Institute.
3. PDQ Adult Treatment Editorial Board. Malignant Mesothelioma Treatment (PDQ®), Health Professional Version. National Cancer Institute. Updated 2025.
4. Kindler HL, Ismaila N, Bazhenova L, et al. Treatment of Pleural Mesothelioma: ASCO Guideline Update. Journal of Clinical Oncology. 2025;43(8):1006–1038. doi:10.1200/JCO-24-02425.
5. Gill RR, Nowak AK, Giroux DJ, et al. The International Association for the Study of Lung Cancer Mesothelioma Staging Project: Proposals for Revisions of the T Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Pleural Mesothelioma. Journal of Thoracic Oncology. 2024;19:1310–1325.
6. Bille A, Ripley RT, Giroux DJ, et al. Proposals for the N Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Pleural Mesothelioma. Journal of Thoracic Oncology. 2024;19:1326–1338.
7. Nowak AK, Giroux DJ, Eisele M, et al. Proposal for Revision of the TNM Stage Groupings in the Forthcoming Ninth Edition of the TNM Classification for Pleural Mesothelioma. Journal of Thoracic Oncology. 2024;19:1339–1351.
8. Kindler HL, Rosenthal A, Giroux DJ, et al. Proposals for the M Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Pleural Mesothelioma. Journal of Thoracic Oncology. 2024;19:1564–1577.
9. Baas P, Scherpereel A, Nowak AK, et al. First-line nivolumab plus ipilimumab in unresectable malignant pleural mesothelioma: CheckMate 743. The Lancet. 2021;397:375–386. doi:10.1016/S0140-6736(20)32714-8.
10. Scherpereel A, Baas P, Nowak AK, et al. Five-Year Clinical Outcomes With Nivolumab Plus Ipilimumab Versus Chemotherapy as First-Line Treatment for Unresectable Pleural Mesothelioma in CheckMate 743. Journal of Clinical Oncology. 2026;44:742–749. doi:10.1200/JCO-25-01328.
11. U.S. Food and Drug Administration. FDA approval of nivolumab in combination with ipilimumab for first-line treatment of unresectable malignant pleural mesothelioma. 2020.
12. Chu Q, Perrone F, Greillier L, et al. Pembrolizumab plus chemotherapy versus chemotherapy in untreated advanced pleural mesothelioma: a phase 3 randomized trial. The Lancet. 2023. doi:10.1016/S0140-6736(23)01613-6.
13. U.S. Food and Drug Administration. FDA approves pembrolizumab with pemetrexed and platinum chemotherapy for unresectable advanced or metastatic malignant pleural mesothelioma. September 17, 2024.
14. Lim E, Waller D, Lau K, et al. Extended pleurectomy decortication and chemotherapy versus chemotherapy alone for pleural mesothelioma (MARS 2): a phase 3 randomized controlled trial. Lancet Respiratory Medicine. 2024;12:457–466. doi:10.1016/S2213-2600(24)00119-X.
15. American Cancer Society. Stages of Mesothelioma. Updated February 3, 2026.
16. American Cancer Society. Survival Rates for Pleural Mesothelioma. Updated February 3, 2026.
17. Husain AN, Chapel DB, Attanoos R, et al. Guidelines for Pathologic Diagnosis of Mesothelioma: 2023 Update of the Consensus Statement From the International Mesothelioma Interest Group. Archives of Pathology & Laboratory Medicine. 2024;148(11):1251–1271. doi:10.5858/arpa.2023-0304-RA.

Peritoneal Mesothelioma at a Glance

What Is Peritoneal Mesothelioma?

The peritoneum is a thin membrane that lines the inside of the abdomen and covers many abdominal organs.

Peritoneal mesothelioma begins when mesothelial cells in this lining become malignant. Rather than forming one isolated mass, invasive disease commonly spreads across multiple peritoneal surfaces.

The term diffuse malignant peritoneal mesothelioma, or DMPM, has traditionally been used for the invasive form of the disease. Modern pathology also recognizes several other mesothelial lesions of the abdomen that have very different behavior and should not be managed as invasive mesothelioma.

Peritoneal and pleural mesothelioma share some biological characteristics, but they are not interchangeable diseases. Evidence from pleural-mesothelioma trials should therefore not automatically be assumed to apply to tumors arising in the abdomen.

How Common Is Peritoneal Mesothelioma?

Peritoneal mesothelioma is extremely rare.

Current U.S. consensus literature estimates an incidence of approximately 0.1 cases per 100,000 people, corresponding to roughly 300–400 new diagnoses each year in the United States. Pleural mesothelioma remains substantially more common.

Because relatively few patients develop peritoneal disease, much of the evidence guiding treatment comes from specialized referral centers, retrospective cohorts, and expert consensus rather than large randomized phase III trials.

This limitation should be considered when interpreting treatment outcomes and survival statistics.

What Causes Peritoneal Mesothelioma?

Asbestos exposure

Asbestos is the best-established environmental risk factor for peritoneal mesothelioma.

Asbestos refers to a group of naturally occurring mineral fibers that were historically used in construction, insulation, shipbuilding, and many industrial products.

When asbestos-containing materials are disturbed, microscopic fibers may become airborne and be inhaled. Some fibers can remain in the body for many years and contribute to biological changes associated with mesothelioma development.

However, the association with asbestos is less consistently documented in peritoneal mesothelioma than in pleural mesothelioma. Some people diagnosed with peritoneal disease have no recognized history of asbestos exposure.

A history of exposure may inform epidemiologic understanding, but it alone cannot confirm or exclude the diagnosis. Pathologic diagnosis relies on morphologic, immunohistochemical, and, when needed, molecular findings. Our asbestos exposure guide covers this topic in more detail.

Does smoking cause peritoneal mesothelioma?

Smoking is not considered an established cause of mesothelioma.

While smoking is a significant risk factor for several cancers, especially lung cancer, it is not considered a cause of peritoneal mesothelioma.

Genetic susceptibility

Inherited cancer-predisposition variants contribute to mesothelioma risk in some patients.

The best-known example involves BAP1, a tumor-suppressor gene associated with BAP1 tumor predisposition syndrome.

Current ASCO guidance recommends that all patients with mesothelioma be offered germline testing. Patients offered testing should also be offered pretest genetic counseling with a qualified health professional.

Symptoms of Peritoneal Mesothelioma

Symptoms can develop gradually and depend partly on the amount and location of disease within the abdomen.

Common presentations may include:

• increasing abdominal size or swelling;
• abdominal discomfort or pain;
• ascites, or fluid accumulation in the abdomen;
• reduced appetite;
• feeling full after eating only a small amount;
• unintended weight loss;
• nausea;
• constipation or other changes in bowel function;
• fatigue.

Some patients are first evaluated after an imaging study performed for another reason reveals ascites, peritoneal thickening, nodules or abnormal omental tissue.

These findings are not specific to mesothelioma. Gastrointestinal disorders, liver disease, inflammatory conditions and other cancers can produce similar symptoms.

Persistent or unexplained abdominal swelling, pain, appetite changes, or weight loss should be evaluated by a healthcare professional rather than attributed to mesothelioma based solely on symptoms. Our symptoms guide covers the broader range of possible signs across all mesothelioma types.

How Peritoneal Mesothelioma Is Diagnosed

Diagnosis usually requires several complementary steps. Our diagnosis guide covers this process in more detail.

Medical history and examination

The initial evaluation typically includes symptoms, medical and surgical history, overall health, and possible occupational or environmental exposure to asbestos.

A known exposure history may raise clinical suspicion, but lack of a recalled exposure does not rule out the disease.

CT imaging

Contrast-enhanced CT of the abdomen and pelvis is commonly used when a peritoneal malignancy is suspected.

Possible findings include:

• ascites;
• peritoneal thickening;
• peritoneal nodules or masses;
• omental involvement;
• bowel or mesenteric involvement;
• enlarged lymph nodes;
• disease outside the abdominal cavity.

Imaging also assists specialists in assessing disease distribution and determining whether complete or near-complete surgical cytoreduction is technically feasible.

However, CT findings alone cannot definitively diagnose peritoneal mesothelioma.

MRI and PET/CT

MRI may provide additional anatomical detail in selected patients.

PET/CT can sometimes help evaluate metabolically active disease or possible disease beyond the peritoneal cavity.

Neither test substitutes for a tissue diagnosis. Our imaging tests guide covers CT, PET, and MRI in more detail.

Ascitic fluid

Some patients undergo paracentesis to remove abdominal fluid.

The procedure may relieve symptoms and allows the fluid to be examined for malignant cells.

However, cytology alone may be insufficient to distinguish peritoneal mesothelioma from other malignancies or to determine the full histologic pattern. Obtaining adequate tissue is often necessary.

Biopsy

Tissue may be obtained through:

• image-guided core biopsy;
• laparoscopy;
• or another surgical biopsy procedure.

Laparoscopy can allow direct inspection of peritoneal surfaces, collection of multiple tissue samples and, in selected cases, assessment of disease distribution before major cytoreductive surgery.

The optimal biopsy method depends on imaging findings, overall health, and the planned treatment strategy. Our tests and biopsy guide covers these procedures in more detail.

How Pathologists Confirm Peritoneal Mesothelioma

Peritoneal mesothelioma can resemble other tumors, particularly cancers that have spread to the peritoneum from the ovaries, gastrointestinal tract or other organs.

Diagnosis therefore depends on the microscopic appearance of the tumor together with a carefully selected panel of immunohistochemical markers that establish mesothelial lineage and help exclude competing diagnoses. IMIG guidance emphasizes that diagnosis should be based on adequate tissue and appropriate morphologic, immunohistochemical, and clinical-radiologic correlation.

BAP1, MTAP and CDKN2A

Additional tests may help distinguish malignant mesothelioma from benign or reactive mesothelial proliferations.

These can include:

• BAP1 immunohistochemistry;
• MTAP immunohistochemistry;
• CDKN2A fluorescence in situ hybridization, or FISH.

Loss of nuclear BAP1 can be particularly useful in peritoneal mesothelial lesions.

An important peritoneal-specific distinction is that MTAP loss and CDKN2A homozygous deletion occur much less often in peritoneal than in pleural mesothelioma. IMIG reports MTAP loss in roughly 5%–10% and CDKN2A homozygous deletion in approximately 10%–15% of peritoneal mesotheliomas. A normal result therefore does not exclude malignancy.

These tests should be interpreted within the context of a comprehensive pathology assessment, not as standalone cancer tests.

Not Every Peritoneal Mesothelial Tumor Is Malignant Mesothelioma

This distinction is especially important in abdominal pathology.

Other mesothelial lesions include well-differentiated papillary mesothelial tumor, or WDPMT, and peritoneal inclusion cysts. These conditions have different biological behavior and treatment approaches from diffuse invasive peritoneal mesothelioma.

Pathology reports should specify the exact tumor entity rather than using the broad term “mesothelioma” without proper qualification.

When the diagnosis is uncertain, specialist pathology review is particularly valuable before major surgery or systemic treatment.

Histologic Types of Peritoneal Mesothelioma

The major invasive histologic categories are:

IMIG notes that sarcomatoid histology accounts for less than 5% of peritoneal mesotheliomas, while biphasic tumors account for roughly 10%–20%.

Histology influences prognosis and treatment strategy, but it is only one aspect of the clinical assessment. Disease burden, lymph-node involvement, extra-abdominal disease, potential for cytoreduction, performance status, and overall health are also critical.

Genetic Counseling and Germline Testing

Genetics has become an increasingly important part of modern mesothelioma care.

The 2025 ASCO guideline recommends that all patients with mesothelioma be offered germline testing and that patients offered testing also be offered pretest genetic counseling by a qualified health professional.

Testing may identify inherited pathogenic variants involving BAP1 or other genes associated with hereditary cancer risk.

A positive result may have implications for:

• assessment of additional cancer risks;
• future cancer surveillance;
• biological relatives who may carry the same inherited variant;
• prognosis in selected circumstances;
• and potentially clinical-trial eligibility.

Germline testing differs from tumor-only genomic sequencing. If tumor sequencing indicates a possible inherited alteration, confirmatory germline testing and genetic counseling are recommended.

How Is Peritoneal Mesothelioma Staged?

Peritoneal mesothelioma should not simply be staged with the AJCC pleural mesothelioma Stage I–IV system.

A research-based TNM model has been proposed for diffuse malignant peritoneal mesothelioma using:

• peritoneal tumor burden;
• lymph-node involvement;
• and distant metastases.

However, this system has not become a universally used clinical equivalent of the AJCC pleural staging system. Our mesothelioma stages guide covers how the AJCC system is used for pleural disease.

For practical treatment planning, specialists often focus instead on:

• histology;
• distribution of disease;
• the Peritoneal Cancer Index;
• lymph-node involvement;
• extra-abdominal disease;
• surgical fitness;
• and the likelihood of achieving complete cytoreduction.

Understanding the Peritoneal Cancer Index

The Peritoneal Cancer Index, or PCI, is a surgical-oncology tool used to describe the extent and distribution of peritoneal tumor.

It considers disease in different regions of the abdomen together with the size of tumor deposits.

In general, increasing PCI reflects a greater volume or broader distribution of peritoneal disease.

However, PCI is not a sole determinant for treatment decisions.

Two patients with similar PCI values may have very different surgical options depending on:

• where the tumor is located;
• involvement of the small bowel or mesentery;
• histology;
• lymph-node disease;
• disease outside the abdomen;
• performance status;
• and whether complete cytoreduction appears achievable.

How Specialists Assess Treatment Risk

Treatment of Peritoneal Mesothelioma

There is no single treatment plan appropriate for every patient.

Treatment planning may consider:

• histologic subtype;
• peritoneal tumor burden;
• likelihood of complete cytoreduction;
• lymph-node disease;
• disease outside the abdomen;
• performance status;
• medical fitness for major surgery;
• previous treatment;
• symptoms;
• patient preferences;
• and clinical-trial availability.

Current consensus emphasizes multidisciplinary assessment and recognizes that several key questions, especially regarding the optimal timing of systemic therapy in relation to surgery, remain unresolved. Our treatment guide covers the full range of approaches used across all mesothelioma types.

Cytoreductive Surgery

Cytoreductive surgery, or CRS, aims to remove all or nearly all visible peritoneal tumor that can be safely removed.

It is not one standardized operation.

Depending on where the disease is located, surgery may involve removal of affected peritoneal surfaces and, when necessary, portions of involved abdominal organs.

The goal is commonly described as complete or near-complete macroscopic cytoreduction.

Completeness of cytoreduction is one of the strongest prognostic factors consistently identified in specialist surgical series.

However, CRS is a major operation and may not be appropriate for all patients.

What Is HIPEC?

HIPEC stands for hyperthermic intraperitoneal chemotherapy.

After cytoreductive surgery, heated chemotherapy is circulated inside the abdominal cavity while the patient remains in the operating room.

The goal is to expose microscopic residual tumor cells within the peritoneal cavity to chemotherapy after as much visible tumor as possible has been removed.

HIPEC therefore works as part of a combined CRS-HIPEC strategy rather than as a substitute for cytoreductive surgery.

Specialist centers may use varying chemotherapy drugs and protocols. No universally standardized HIPEC regimen exists for peritoneal mesothelioma.

Who May Be Considered for CRS-HIPEC?

Patient selection is critical.

Factors considered by specialist teams can include:

• whether disease is confined mainly to the abdomen;
• epithelioid versus non-epithelioid histology;
• amount and distribution of tumor;
• bowel and mesenteric involvement;
• lymph-node disease;
• distant metastases;
• likelihood of complete cytoreduction;
• functional status;
• cardiovascular and general surgical fitness;
• nutrition;
• and patient preferences.

Patients not eligible for CRS-HIPEC may still have options including systemic therapy, clinical trials, and symptom management.

Unresectable disease does not mean untreatable disease.

How Strong Is the Evidence for CRS-HIPEC?

CRS-HIPEC has become the major specialist locoregional treatment for appropriately selected patients with diffuse peritoneal mesothelioma.

A multisocietal consensus supports CRS-HIPEC for carefully selected patients, while also emphasizing that the certainty of evidence is limited because randomized trials are lacking and much of the survival evidence comes from observational specialist-center studies.

This distinction matters.

CRS-HIPEC should neither be dismissed as an unproven experimental procedure nor presented as a treatment proven by randomized trials to benefit every patient.

Selection is central to the outcome.

What Are the Risks of CRS-HIPEC?

CRS-HIPEC is a major abdominal treatment and can involve significant complications.

In a multi-institutional series of 401 patients summarized by the NCI, 31% experienced grade 3–4 complications and 2% died in the perioperative period. The same cohort included highly selected patients treated at centers experienced with cytoreductive surgery.

Potential risks vary based on the extent of surgery and individual health, and should be discussed with the surgical team.

These risks highlight the need to balance potential long-term benefits with operative morbidity, rather than focusing solely on tumor removal.

Systemic Chemotherapy

Systemic therapy can be important when:

• surgery is not appropriate;
• complete cytoreduction is unlikely;
• disease is higher risk;
• cancer has spread outside the abdomen;
• disease recurs;
• or systemic treatment forms part of a multimodality strategy.

For epithelioid peritoneal mesothelioma, current consensus guidance includes pemetrexed plus a platinum drug, usually cisplatin or carboplatin, with consideration of bevacizumab in appropriately selected patients.

Evidence for chemotherapy specific to peritoneal mesothelioma is much less extensive than for many common cancers.

The optimal timing of chemotherapy in relation to CRS-HIPEC remains uncertain.

Immunotherapy

Immune-checkpoint inhibitors have become increasingly important in mesothelioma treatment, but the evidence base for peritoneal mesothelioma is smaller than for pleural disease.

The pivotal CheckMate 743 trial that established nivolumab plus ipilimumab enrolled patients with pleural mesothelioma, not peritoneal mesothelioma. Its survival results therefore should not simply be transferred to patients with disease arising in the abdomen.

Nevertheless, newer peritoneal-specific consensus guidance incorporates immunotherapy into systemic-treatment pathways. For epithelioid disease, nivolumab plus ipilimumab is listed among preferred first-line options alongside platinum-pemetrexed-based treatment and clinical-trial enrollment. For biphasic or sarcomatoid peritoneal mesothelioma, the consensus favors nivolumab plus ipilimumab as a preferred first-line systemic approach.

The important limitation is that these recommendations partly rely on extrapolation from pleural mesothelioma and smaller real-world peritoneal datasets rather than a dedicated randomized phase III peritoneal-mesothelioma trial.

In the United States, the FDA-labeled mesothelioma indication for nivolumab plus ipilimumab is specifically unresectable malignant pleural mesothelioma, not peritoneal mesothelioma.

Pembrolizumab: Peritoneal-Specific Evidence

There is also limited evidence specific to pembrolizumab in peritoneal disease.

A retrospective two-center study evaluated 24 adults with diffuse peritoneal mesothelioma treated with pembrolizumab.

Among evaluable patients, approximately:

• 21% achieved a partial response;
• 53% had stable disease;
• median progression-free survival was 4.9 months;
• median overall survival from pembrolizumab initiation was 20.9 months.

Most patients had prior systemic chemotherapy, and the study lacked a randomized control group.

These findings show clinical activity but do not establish pembrolizumab as the universally preferred treatment.

The FDA approval of pembrolizumab with pemetrexed and platinum chemotherapy is specifically for unresectable advanced or metastatic malignant pleural mesothelioma, so that pleural indication should not be presented as a peritoneal-specific approval.

Is Radiation Therapy Used?

Radiation therapy has a limited role in diffuse peritoneal mesothelioma.

Treating large areas of the abdomen can be difficult because sensitive organs—including the bowel, liver and kidneys—may be nearby.

Radiation may nevertheless be considered in selected situations for localized symptom control or treatment of a specific disease site.

The use of radiation therapy should be individualized based on disease distribution and prior treatments.

Managing Ascites and Other Symptoms

Cancer-directed treatment and symptom-directed care should work together.

Ascites

Ascites can cause:

• increasing abdominal size;
• pressure or discomfort;
• reduced appetite;
• early fullness;
• and sometimes shortness of breath.

Paracentesis can remove fluid and provide symptom relief in selected patients.

When ascites repeatedly returns, additional management depends on the underlying disease, anticipated treatment and individual circumstances.

Pain, nutrition and digestive symptoms

Supportive treatment can also address:

• abdominal pain;
• nausea;
• constipation or diarrhea;
• poor appetite;
• unintended weight loss;
• fatigue;
• sleep problems;
• functional limitations;
• emotional distress.

Nutritional support is especially important for patients whose abdominal disease or treatment impairs their ability to eat.

Palliative Care Can Be Used During Active Treatment

Palliative care is not the same as hospice.

Palliative-care specialists focus on symptoms, quality of life, communication and support for patients and families.

Palliative care may be provided alongside ongoing anticancer treatments, including systemic therapy or surgery.

Current peritoneal-mesothelioma consensus guidance also emphasizes establishing patient support services and using palliative care when appropriate.

What Happens if Peritoneal Mesothelioma Comes Back?

Recurrence does not necessarily mean all previous treatment options are permanently unavailable.

Specialists may consider:

• location of recurrent disease;
• time since previous treatment;
• previous CRS-HIPEC;
• current tumor burden;
• histology;
• general health;
• previous systemic therapies;
• whether another meaningful cytoreduction could be achieved;
• and available clinical trials.

Some carefully selected patients may be considered for additional locoregional treatment, while others may receive systemic therapy or symptom-focused care.

Given the limited evidence for recurrence strategies, multidisciplinary specialist review is particularly important.

Clinical Trials

Clinical trials are particularly important in peritoneal mesothelioma because relatively few prospective trials have focused specifically on this disease.

The current Peritoneal Surface Malignancies Consortium consensus reached unanimous support for considering clinical trial enrollment, and its systemic treatment recommendations encourage trial consideration throughout the treatment pathway.

Research areas include:

• immune-checkpoint inhibitors;
• new immunotherapy combinations;
• targeted treatments;
• biomarker-directed therapy;
• intraperitoneal therapies;
• optimization of CRS-HIPEC;
• treatment sequencing.

Eligibility depends on factors such as histology, previous treatment, disease distribution, molecular findings, organ function, and performance status.

Eligibility for clinical trials must be determined by a healthcare professional; a website cannot assess individual eligibility. Talk to your oncology team and check official registries like ClinicalTrials.gov.

Peritoneal Mesothelioma Prognosis

Prognosis varies considerably between patients.

Important factors can include:

• histologic subtype;
• peritoneal tumor burden;
• lymph-node involvement;
• extra-abdominal disease;
• ability to achieve complete or near-complete cytoreduction;
• performance status;
• overall health;
• and response to treatment.

Epithelioid histology, absence of lymph-node metastases and successful cytoreduction have consistently been associated with more favorable outcomes in surgical series.

Survival after CRS-HIPEC

One of the largest multi-institutional datasets summarized by the NCI included 401 patients treated with cytoreductive surgery; 92% also received HIPEC.

In that selected surgical population:

• median overall survival was 53 months;
• estimated 3-year survival was 60%;
• estimated 5-year survival was 47%.

Better outcomes were associated with epithelioid histology, absence of lymph-node metastases, complete or near-complete cytoreduction and use of HIPEC.

Our mesothelioma prognosis guide covers survival data and terminology in more detail.

Why Specialist Care Matters

Peritoneal mesothelioma sits at the intersection of several specialties.

A multidisciplinary team may include:

• surgical oncology;
• medical oncology;
• gastrointestinal oncology;
• abdominal radiology;
• pathology;
• genetics;
• nutrition;
• palliative care.

Specialist evaluation can help answer critical questions:

• Has an experienced pathologist confirmed the diagnosis?
• Is this invasive mesothelioma or another mesothelial lesion?
• What is the histologic subtype?
• How extensive is the disease?
• Is it confined primarily to the abdomen?
• What is the expected likelihood of complete cytoreduction?
• Is CRS-HIPEC appropriate?
• Should systemic therapy be used?
• Is immunotherapy appropriate in this setting?
• Should treatment be given before or after surgery?
• Is a clinical trial available?

Obtaining a second opinion does not require transferring all future care to another hospital. A specialist center can review pathology, imaging, and treatment plans while some care continues locally.

Questions to Ask Your Medical Team

1. Has my biopsy been reviewed by a pathologist experienced in mesothelioma?
2. Is this diffuse invasive peritoneal mesothelioma or another mesothelial tumor?
3. What histologic subtype do I have?
4. Is disease confined mainly to the abdomen?
5. Are lymph nodes or distant organs involved?
6. How extensive is the peritoneal disease?
7. Has my Peritoneal Cancer Index been assessed or estimated?
8. Do you believe complete or near-complete cytoreduction is achievable?
9. Am I a candidate for CRS-HIPEC?
10. How much experience does this center have treating peritoneal mesothelioma?
11. What are the major risks of CRS-HIPEC in my situation?
12. Should systemic treatment be considered before or after surgery?
13. If surgery is not appropriate, which systemic treatments should we discuss?
14. How strong is the evidence for immunotherapy specifically in peritoneal mesothelioma?
15. Should I have germline genetic testing?
16. Are there clinical trials relevant to my diagnosis?
17. What can be done now to manage ascites, pain, appetite problems, or other symptoms?
18. Would a second opinion at a peritoneal-surface malignancy center be useful?

Frequently Asked Questions

References

1. Brown LM, Wilkins SG, Bansal VV, et al. Consensus Guideline for the Management of Peritoneal Mesothelioma. Annals of Surgical Oncology. 2026;33(6):5125–5141. doi:10.1245/s10434-025-17358-x.
2. Kusamura S, Cinquini M, Morris D, et al. Multisocietal Consensus on the Use of Cytoreductive Surgery and HIPEC for the Treatment of Diffuse Malignant Peritoneal Mesothelioma: A GRADE Approach for Evidence Evaluation and Recommendation. Journal of Surgical Oncology. 2025;131(5):810–815. doi:10.1002/jso.27947.
3. PDQ Adult Treatment Editorial Board. Malignant Mesothelioma Treatment (PDQ®), Health Professional Version. National Cancer Institute.
4. Husain AN, Chapel DB, Attanoos R, et al. Guidelines for Pathologic Diagnosis of Mesothelioma: 2023 Update of the Consensus Statement From the International Mesothelioma Interest Group. Archives of Pathology & Laboratory Medicine. 2024;148(11):1251–1271. doi:10.5858/arpa.2023-0304-RA.
5. Kindler HL, Ismaila N, Bazhenova L, et al. Treatment of Pleural Mesothelioma: ASCO Guideline Update. Journal of Clinical Oncology. 2025;43(8):1006–1038. doi:10.1200/JCO-24-02425. Germline-testing recommendations apply broadly to patients with mesothelioma.
6. Marmarelis ME, Wang X, Roshkovan L, et al. Clinical Outcomes Associated With Pembrolizumab Monotherapy Among Adults With Diffuse Malignant Peritoneal Mesothelioma. JAMA Network Open. 2023;6(3):e232526. doi:10.1001/jamanetworkopen.2023.2526.
7. Boffetta P. Epidemiology of Peritoneal Mesothelioma: A Review. Annals of Oncology. 2007;18(6):985–990. doi:10.1093/annonc/mdl345.
8. Broeckx G, Pauwels P. Malignant Peritoneal Mesothelioma: A Review. Translational Lung Cancer Research. 2018;7(5):537–542. doi:10.21037/tlcr.2018.10.04.
9. U.S. Food and Drug Administration. FDA approves nivolumab and ipilimumab for unresectable malignant pleural mesothelioma. October 2, 2020.
10. U.S. Food and Drug Administration. FDA approves pembrolizumab with chemotherapy for unresectable advanced or metastatic malignant pleural mesothelioma. September 17, 2024. FDA.gov.
11. Yan TD, Deraco M, Baratti D, et al. Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy for Malignant Peritoneal Mesothelioma: Multi-Institutional Experience. Journal of Clinical Oncology. 2009;27(36):6237–6242. doi:10.1200/JCO.2009.23.9640.