Mesothelioma is a cancer of tissue called the mesothelium, a lining that covers and protects many of the body’s internal organs, including the lungs, abdominal organs, and heart. It is most commonly caused by exposure to asbestos – building materials that were once frequently used for insulation and fire prevention until being banned in most developed countries beginning in the late 1980s.

Because males historically have been more likely to work in occupations that might lead to asbestos exposure, the cancer is about three times more common in men than in women. In addition, because mesothelioma develops two to four decades after asbestos exposure, there are about ten times as many cases in men over age 64 as there are in men in their 30s.

Types of Mesothelioma

About 2,000 to 3,000 new cases of mesothelioma are diagnosed each year in the United States. Of these, 75 percent of cases affect the sac that protects the lungs, called the pleura. This type of mesothelioma is known as pleural mesothelioma.

In about 10 to 20 percent of cases, mesothelioma affects the tissue that surrounds abdominal organs, called the peritoneal membrane, causing what is known as peritoneal mesothelioma.

Less common types of mesothelioma include testicular mesothelioma and pericardial mesothelioma, which affects the lining surrounding the heart.

Risk Factors

People in occupations that once involved exposure to asbestos, such as mining, milling, construction, plumbing, heating, insulation, carpentry, and electrical and shipyard work, generally have had greater exposure to asbestos than those in other occupations and are therefore at higher risk of mesothelioma.

Family members of people who worked in these industries are also at increased risk because they may have had indirect exposure to asbestos through clothing and hair.

Other risk factors for mesothelioma are an inherited mutation in the gene BAP1 and prior treatment with radiation therapy for other cancers, such as Hodgkin lymphoma.


Most people with pleural mesothelioma experience shortness of breath caused by the buildup of fluid in the membrane surrounding the lung, known as pleural effusion. Pain in the chest area resulting from the tumor invading the chest wall is also common. Other symptoms that can develop include weight loss, fatigue, and night sweats.

People with peritoneal mesothelioma may experience abdominal swelling due to fluid buildup in the abdomen (a condition called ascites), pain in the abdominal area, diarrhea, or constipation.

While these symptoms may be caused by other conditions, if you experience any of them and have been exposed to asbestos at some point, we recommend that you speak with your doctor.