Mesothelioma (or, more precisely, malignant mesothelioma) is a rare form of cancer that develops from cells of the mesothelium, the protective lining that covers many of the internal organs of the body. Mesothelioma is most commonly caused by exposure to asbestos. The most common anatomical site for mesothelioma is the pleura (the outer lining of the lungs and internal chest wall), but it can also arise in the peritoneum (the lining of the abdominal cavity), the pericardium (the sac that surrounds the heart), or the tunica ******lis (a sac that surrounds the testis).
Most people who develop mesothelioma have worked in jobs such as miners where they inhaled or ingested asbestos fibers, or were exposed to airborne asbestos dust and fibers in other ways. Washing clothes of a family member who worked with asbestos also creates a risk for developing mesothelioma.