Mesothelioma is a cancer that begins in the mesothelium—the thin layer of tissue covering certain organs and body cavities. It most often forms in the pleura, the lining around the lungs and inside the chest wall. It can also begin in the peritoneum, which lines the abdominal cavity. Far rarer forms affect tissue around the heart or testicles.
Asbestos exposure is the major known risk factor for adult mesothelioma. The disease often develops many years after exposure, which can make it difficult to remember when and where contact occurred.
Key takeaways
- Mesothelioma is not the same disease as lung cancer, although both can affect the chest and may be associated with asbestos.
- Pleural mesothelioma is the most common form; peritoneal mesothelioma begins in the abdomen.
- Asbestos exposure can occur at work, during military service, at home or through fibers carried home by another person.
- Imaging may reveal an abnormality, but doctors generally need tissue examined by a pathologist to confirm the diagnosis.
- Treatment is individualized and may involve surgery, chemotherapy, immunotherapy, radiation, supportive care or a clinical trial.
Where mesothelioma develops
Pleural mesothelioma
Pleural mesothelioma begins in the tissue surrounding the lungs. Possible symptoms include shortness of breath, chest pain, cough and fluid around a lung. These symptoms are not specific to mesothelioma and can have many other causes.
Peritoneal mesothelioma
Peritoneal mesothelioma develops in the lining of the abdominal cavity. Possible symptoms include abdominal swelling or pain, appetite changes, nausea, bowel changes and unexplained weight loss.
Rare locations
Pericardial mesothelioma begins in tissue around the heart. Mesothelioma of the tunica vaginalis affects tissue surrounding a testicle. Because these cancers are very rare, evaluation at a center experienced with mesothelioma may be especially useful.
What causes mesothelioma?
Asbestos is a group of naturally occurring mineral fibers once widely used for heat resistance, insulation and durability. When asbestos-containing material is damaged or disturbed, microscopic fibers may become airborne. Inhaled fibers can remain in the body and contribute to inflammation and cellular damage over time.
Not everyone exposed to asbestos develops mesothelioma, and some people diagnosed with mesothelioma do not know when they were exposed. Risk is influenced by factors including the amount, duration and type of exposure and individual susceptibility.
Smoking is not considered a cause of mesothelioma. However, smoking and asbestos exposure together greatly increase lung-cancer risk. Anyone who smokes can ask a clinician about evidence-based help to quit.
How long can mesothelioma take to develop?
Asbestos-related diseases typically have long latency periods. Symptoms may not appear until decades after exposure. A diagnosis today may therefore relate to work or other circumstances from many years earlier.
How doctors diagnose mesothelioma
The evaluation may include a medical and occupational history, physical examination, imaging such as chest X-ray or CT, and procedures to collect fluid or tissue. A biopsy allows a pathologist to examine tissue and is central to confirming mesothelioma and distinguishing it from other cancers.
Because mesothelioma is rare and can resemble other diseases, patients may consider a pathology review or second opinion at a center experienced with mesothelioma.
Treatment overview
Treatment decisions depend on where the cancer began, stage, cell type, whether surgery is feasible, heart and lung health, other medical conditions and the patient’s goals. A plan may combine treatments and supportive care.
Explore mesothelioma treatment
What to do after a diagnosis
- Ask for copies of pathology, imaging, treatment notes and a current medication list.
- Confirm the exact type, location, cell type and stage recorded by the care team.
- Ask whether review by a multidisciplinary team or a mesothelioma center is appropriate.
- Discuss treatment goals, benefits, risks, alternatives and clinical trials.
- Begin writing down employment, military, home-renovation and family exposure history without disturbing suspected asbestos material.
- If considering legal advice, remember that filing deadlines differ by state.
Sources
- National Cancer Institute. What Is Mesothelioma? Updated May 16, 2025.
- National Cancer Institute. Mesothelioma Causes and Risk Factors Updated May 16, 2025.
- National Cancer Institute. Asbestos Exposure and Cancer Risk.
- Agency for Toxic Substances and Disease Registry. Health Effects of Asbestos Updated August 12, 2024.
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