What is mesothelioma?
Mesothelioma is a cancer that starts in the mesothelium, the thin layer of tissue that lines the chest, the abdomen, the space around the heart, and the testicles. It is rare, and most cases are linked to asbestos.
Last reviewed October 27, 2026 against the sources listed at the end of this page.
In short
- Mesothelioma starts in the mesothelium, a thin lining that protects the lungs, abdomen, heart, and testicles.
- NCI says most mesotheliomas are thought to be caused by asbestos exposure.
- The gap between first exposure and diagnosis is usually 20 to 50 years, according to the American Cancer Society.
- Pleural mesothelioma (in the chest) makes up more than 8 out of 10 cases.
- Most people exposed to asbestos never develop mesothelioma, but the risk does not fade after exposure stops.
The lining where it starts
Special cells called mesothelial cells form a thin, slippery lining inside the body. The American Cancer Society explains that this lining makes a small amount of fluid so organs can slide against each other, for example when the lungs expand with each breath. The lining has a different name in each part of the body:
| Lining | Where it is | Cancer that starts there |
|---|---|---|
| Pleura | Around the lungs and inside the chest wall | Pleural mesothelioma |
| Peritoneum | Inside the abdomen (belly) and over most of its organs | Peritoneal mesothelioma |
| Pericardium | Around the heart | Pericardial mesothelioma |
| Tunica vaginalis | Around the testicles | Testicular mesothelioma |
Doctors used to call the disease "malignant mesothelioma." Today it is usually just called mesothelioma. Each type is explained on the types of mesothelioma page.
The link to asbestos
Asbestos is the name for six natural minerals made of tiny fibers that resist heat, fire, and chemicals. NCI notes that asbestos was used widely in insulation, roofing, fireproofing, cement, ship boilers and steam pipes, brakes and clutches, and floor and ceiling tiles. When those materials are disturbed, fibers float into the air and can be breathed in or swallowed. Some lodge in the lining of the chest or abdomen and stay there for decades.
According to NCI, most mesotheliomas are thought to be caused by asbestos exposure. The International Agency for Research on Cancer and U.S. health agencies classify asbestos as a known cause of cancer in people.
Other risk factors named by the American Cancer Society include erionite (an asbestos-like mineral found in some rock and soil), past high-dose radiation therapy to the chest or abdomen, older age, and inherited changes in the BAP1 gene. Smoking raises the risk of lung cancer after asbestos exposure a great deal, but NCI notes that it does not appear to raise the risk of mesothelioma.
Why it shows up so late
The American Cancer Society says the time between first asbestos exposure and a mesothelioma diagnosis is usually 20 to 50 years, and the risk does not go down after exposure stops. That is why many people diagnosed today were exposed in the 1950s through the 1980s, in shipyards, the military, construction, factories, and power plants. It is also why people often cannot remember the details at first. Our asbestos exposure page lists the jobs and places where exposure was common.
What the cell type means
Pathologists (doctors who examine tissue under a microscope) sort mesothelioma into three main cell types. The American Cancer Society describes them this way:
- Epithelioid: about 6 in 10 cases. It tends to have a better outlook than the other types.
- Sarcomatoid: about 1 in 10 cases. It tends to be harder to treat.
- Biphasic (mixed): has both kinds of cells, about 3 in 10 cases.
The cell type, the location, and the stage all shape treatment choices. See diagnosis and staging and treatment options.
What to do next
If you have been diagnosed, the most useful early steps are usually medical: confirm the diagnosis with a pathologist experienced in mesothelioma and ask about care at a center that treats it often. NCI keeps a list of NCI-designated cancer centers. When you feel ready, start a simple written list of every job, ship, base, and home where asbestos might have been present, with rough dates. That list helps your doctors, and it is the starting point for any VA claim, trust fund claim, or lawsuit.
Tell us what happened. A lawyer from a participating firm can call you to talk through your options.
Start the free reviewCommon questions
Is mesothelioma a type of lung cancer?
No. Pleural mesothelioma grows in the lining around the lungs (the pleura), not in the lung tissue itself. It is diagnosed and treated differently from lung cancer, although asbestos exposure raises the risk of both.
Can you get mesothelioma without working with asbestos?
Yes. The American Cancer Society notes that family members of asbestos workers can be exposed through dust brought home on clothing, and some people are exposed in older buildings. In some people no clear exposure is ever found.
Is mesothelioma contagious or inherited?
It is not contagious. A small number of families carry an inherited change in the BAP1 gene that raises the risk of mesothelioma after asbestos exposure, according to the American Cancer Society and NCI. Genetic counseling can help if several relatives have had it.
This page is general health information, summarized from the sources below. It is not medical advice. Talk with your own doctor or care team about your situation.