What Is Mesothelioma?

Latest federal incidence data show 2,669 new mesothelioma cases in the United States in 2022, which is the most recent year currently available in U.S. Cancer Statistics incidence reporting. Other major cancer references describe mesothelioma as accounting for about 3,000 new diagnoses each year in the United States. CDC

Microscopic examination of chrysotile asbestos fibers, illustrating the needle-like structures that can become embedded in tissue.

Mesothelioma is strongly associated with asbestos exposure. Major public-health and cancer authorities state that asbestos exposure causes most mesothelioma cases, and the disease often develops only after a long latency period measured in decades.

Because of that delay, mesothelioma still occurs even though asbestos use has declined significantly over time. CDC states that mesothelioma incidence rates have been decreasing as fewer people are exposed to asbestos.

Where Mesothelioma Develops

Anatomical representation of the pleura, the primary site for mesothelioma development following inhalation of fibers.

Mesothelioma is usually classified by the part of the body where it begins:

• Pleural mesothelioma develops in the lining around the lungs.
• Peritoneal mesothelioma develops in the lining of the abdomen.
• Pericardial mesothelioma affects the lining around the heart and is rare.
• Testicular mesothelioma affects tissue around the testicles and is also rare.

Pleural mesothelioma accounts for the large majority of cases, while peritoneal mesothelioma is much less common. CDC's current U.S. incidence summary reports that pleural mesothelioma made up 81.0% of malignant mesothelioma cases from 2003 through 2022, while peritoneal mesothelioma accounted for 11.1%.

Why Asbestos Matters

Asbestos is the name for a group of naturally occurring mineral fibers that were widely used in insulation, construction materials, industrial products, and other commercial applications. When asbestos-containing materials are disturbed, tiny fibers can be released and inhaled or swallowed. Those fibers can remain in the body and contribute to disease years later, including mesothelioma. NCI

Long Latency Is Part of the Story

Mesothelioma usually does not appear soon after exposure. Instead, there is often a delay of 20 to 50 years or more between asbestos exposure and diagnosis. That long latency is one reason cases can still appear decades after exposure occurred. American Cancer Society

This delay also contributes to the difficulty of early diagnosis. Symptoms may not appear until the disease is more advanced, and diagnosis generally requires imaging and tissue sampling rather than symptoms alone.

Symptoms and Diagnosis

Symptoms vary depending on where mesothelioma starts.

For pleural mesothelioma, symptoms can include:

• Shortness of breath
• Chest pain
• Pain under the rib cage
• Cough

For peritoneal mesothelioma, symptoms can include:

• Abdominal pain
• Abdominal swelling or fluid buildup
• Nausea
• Unexplained weight loss

Because these symptoms can overlap with many other conditions, doctors usually rely on imaging tests and a biopsy to confirm mesothelioma. American Cancer Society

Treatment at a Glance

Treatment depends on the type and stage of the disease, whether the cancer can be surgically removed, and the patient's overall health. National Cancer Institute treatment guidance notes that care may include surgery, chemotherapy, radiation therapy, immunotherapy, and supportive care, depending on the clinical situation.

Key Takeaway

Mesothelioma is a rare but serious cancer most closely linked to asbestos exposure. Although U.S. incidence rates have declined over time, the disease continues to appear because it often develops decades after exposure. The most common form affects the lining around the lungs, and confirmed diagnosis typically requires both imaging and biopsy.