Malignant mesothelioma is a rare cancer of the lining of the lung (pleural mesothelioma) or the lining of the abdomen (peritoneal mesothelioma). The only known cause of mesothelioma in the U.S. is exposure to asbestos. Mesothelioma has a long latency period, the time between first exposure to asbestos and the diagnosis of the disease. In rare cases the latency period has been as short as 10 to 15 years after the first exposure to asbestos; however, generally mesothelioma occurs between 20 and 40 or more years after an individual's first exposure. Diagnosing mesothelioma is often difficult because the symptoms are similar to those of a number of other conditions.

Benign mesothelioma is a non-cancerous tumor of the pleura (lining of the lung and chest cavity). Nonmalignant mesothelioma is usually a localized tumor that affects men more frequently than women. The tumor may grow to a large size and compress the lung, which then causes the following symptoms: chronic cough, shortness of breath, chest pain, weight loss and cachexia, abdominal swelling and pain due to ascites (a buildup of fluid in the abdominal cavity).

Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face. These symptoms may be caused by mesothelioma or by other, less serious conditions.

Approximately half of mesothelioma patients are asymptomatic (show no symptoms of disease). During a physical examination, a health care provider may notice a clubbed appearance of the fingers in a patient, which is an indication of the exposure/disease.The health care professional may run tests that identify mesothelioma. These tests include a chest x-ray, CT scan of the chest and/or and open lung biopsy.

There is no universally accepted protocol for screening people who have been exposed to asbestos. However some research indicates that serum osteopontin levels might be useful in screening asbestos-exposed people for mesothelioma. The level of soluble mesothelin-related protein is elevated in the serum of about 75% of patients at diagnosis, and it has been suggested that assessing soluble mesothelin-related protein levels may be useful for screening.

Surgery is usually generally necessary for a solitary tumor (if found); however, according to current statistics, the outcome of the surgery is expected to be good with prompt treatment. One of the most common complications though is pleural effusion (fluid escaping into the membranes around the lungs), which can be very serious.

Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fiber in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products.