Types of Mesothelioma

Mesothelioma is classified in two different ways: by where in the body it develops, and by what the cancer cells look like under a microscope. These are not competing systems — doctors use both together to understand a person’s diagnosis and plan care. Someone diagnosed with mesothelioma will typically hear both pieces of information described early on, often together with the extent, or stage, of the disease. This guide explains each type by location, each subtype by cell pattern, and how that classification connects to symptoms, diagnosis, staging, and treatment planning — using figures drawn from the American Cancer Society rather than unsourced estimates.

How Mesothelioma Is Classified

Mesothelioma begins in the mesothelium, a thin layer of specialized cells that lines the chest cavity, the abdominal cavity, the sac around the heart, and — in a much rarer form — the covering layer of the testicles. Because this lining exists in several different places in the body, mesothelioma is first classified by which location it starts in. This is called the anatomical type.

Separately, when a sample of tumor tissue is examined under a microscope, the cancer cells themselves fall into recognizable patterns. This is called the histological subtype, and it follows classification standards used in pathology worldwide, including tumor classification frameworks maintained by the World Health Organization. A person’s diagnosis generally includes both pieces of information: for example, someone might be diagnosed with epithelioid pleural mesothelioma — an anatomical type (pleural) and a histological subtype (epithelioid) together.

Both pieces of information matter for different reasons. The anatomical type affects which organs and structures are involved, which symptoms are more likely, and — as explained below — whether a formal staging system exists. The histological subtype, on the other hand, reflects how the cancer cells themselves are behaving, which can inform how a specialist team thinks about treatment approach and general prognosis patterns. Neither classification on its own tells the full story, which is one reason a multidisciplinary care team typically reviews both together.

Types of Mesothelioma by Location

Comparing Mesothelioma Types

This table describes general patterns reported in medical literature, not individual predictions. Symptoms listed are not unique to mesothelioma and can be caused by many other conditions.

Histological Subtypes

Alongside anatomical location, doctors classify mesothelioma by histological subtype — the pattern the cancer cells form under a microscope. This classification applies across all anatomical types and is a separate system from the location-based one above.

Epithelioid Mesothelioma

Epithelioid mesothelioma is the most common cell pattern, making up about 6 in 10 mesotheliomas according to the American Cancer Society. The cells tend to form organized, cuboidal shapes similar to the cells that make up healthy lining tissue. Epithelioid mesothelioma is a subtype of mesothelioma itself, not a form of lung cancer, regardless of which anatomical location it develops in. Histology can cautiously be considered one of several factors doctors weigh in prognosis and treatment planning, generally alongside stage, extent of disease, and a patient’s overall health.

Sarcomatoid Mesothelioma

Sarcomatoid mesothelioma involves cells with an elongated, spindle-like shape, and accounts for about 1 in 10 mesotheliomas. Response to treatment and typical disease behavior can differ from epithelioid disease, though this describes patterns observed across groups of patients rather than a prediction for any individual. A specialist care team is best placed to explain what a sarcomatoid diagnosis may mean in a specific situation.

Biphasic (Mixed) Mesothelioma

Biphasic mesothelioma contains a mix of both epithelioid and sarcomatoid cell patterns within the same tumor, and makes up the remaining roughly 3 in 10 mesotheliomas. The proportion of each cell pattern present may matter clinically and is something a pathologist notes during review. As with sarcomatoid disease, published survival estimates describe populations, not individuals, so we do not include specific numbers here.

How Type Can Influence Symptoms

Because each anatomical type develops in a different part of the body, the location often shapes which symptoms are most likely to appear first. Pleural disease is more often associated with respiratory symptoms such as breathlessness or cough; peritoneal disease is more often associated with abdominal symptoms such as pain, swelling, or digestive changes; pericardial disease can involve the heart and chest more directly. None of these symptom patterns are unique to mesothelioma — each can be caused by many more common conditions, which is one reason mesothelioma can take time to diagnose. Our symptoms guide covers this in more detail.

How Doctors Determine the Type

Identifying both the anatomical type and histological subtype generally involves several steps working together, rather than any single test on its own:

• Medical history — including any known asbestos exposure and the pattern and duration of symptoms.
• Imaging — such as CT, MRI, or PET scans, to help identify the location and extent of any abnormal tissue.
• Fluid sampling — in some circumstances, fluid that has built up around the lungs or abdomen may be tested.
• Tissue biopsy — a sample of the affected lining is generally an important part of confirming a diagnosis, though the specific approach can vary by individual circumstances.
• Pathological examination — a pathologist examines the tissue sample under a microscope to identify the histological subtype.
• Immunohistochemistry — a laboratory technique that uses special stains to help distinguish mesothelioma from other conditions that can look similar under a microscope.
• Multidisciplinary review — findings are typically reviewed by a team that may include pathologists, radiologists, and oncologists before a diagnosis is finalized.

This is a general description of a diagnostic pathway, not instructions to follow independently. Our diagnosis guide explains this process in more depth.

Type, Staging, and Treatment Planning

Anatomical type affects how mesothelioma is staged. Pleural mesothelioma is the only type with a formal staging system — typically the American Joint Committee on Cancer’s TNM system, which describes the extent of the primary tumor, whether nearby lymph nodes are involved, and whether the cancer has spread elsewhere. Peritoneal and pericardial mesothelioma do not currently have a formal staging system in the same way, though doctors still work to determine the extent of disease using imaging and other findings.

Treatment planning may depend on several factors together: anatomical location, histological subtype, extent of disease, a person’s overall health, symptoms, and personal treatment goals, following assessment by a specialist multidisciplinary team. Broad treatment categories that may be considered include surgery, systemic therapy (such as chemotherapy), radiation therapy, immunotherapy, symptom-directed and supportive care, and — for some peritoneal cases — selected regional approaches. No single option is universally “the best” treatment, and no treatment can be guaranteed to produce a particular outcome; a specialist team weighs these factors for each individual.

Because peritoneal and pericardial mesothelioma do not have a formal staging system, doctors evaluating these types typically rely more heavily on imaging findings, the extent of disease observed during any surgery, and overall clinical judgment when discussing treatment options with a patient. This is a meaningful difference from pleural disease, where a formal stage can more directly inform standard treatment pathways. Read more on our treatment guide and prognosis guide.

Questions to Ask a Specialist

If you or someone you know has been diagnosed with mesothelioma, these questions may help guide a conversation with a care team:

1. What is the anatomical type and histological subtype of this mesothelioma?
2. What tests were used to confirm the diagnosis, and is a second pathology opinion available?
3. Is a formal stage available, or is extent of disease being described in another way?
4. What treatment categories are being considered, and what is the reasoning behind them?
5. Are there clinical trials that may be relevant to this specific type and subtype?
6. What support resources — medical, practical, or financial — are available during treatment?

When to Seek Medical Evaluation

Frequently Asked Questions

Editorial and Medical Review Information

References

1. American Cancer Society. “What Is Malignant Mesothelioma?” cancer.org, reviewed 2024.
2. American Cancer Society. “Key Statistics About Mesothelioma.” cancer.org, reviewed 2025.
3. American Cancer Society. “Mesothelioma Stages.” cancer.org, reviewed 2024.

Related Mesothelioma Resources

• Mesothelioma Overview HubSymptoms, causes, diagnosis, treatment, and prognosis in one place.
• Mesothelioma SymptomsCommon early signs and when to seek evaluation.
• Diagnosis GuideHow imaging, biopsy, and pathology confirm a diagnosis.
• Treatment OptionsSurgery, systemic therapy, radiation, and supportive care.
• Asbestos ExposureHow exposure happens and who is most at risk.
• Find a SpecialistLocate experienced mesothelioma care.