What is malignant mesothelioma?

Asbestos is the only known risk factor for malignant mesothelioma, a cancer that affects the tissue lining the lung (pleura) or abdomen (peritoneum). Malignant mesothelioma is not associated with cigarette smoking but is strongly linked with the degree of asbestos exposure. However, 20% to 40% of patients with malignant mesothelioma have no prior asbestos exposure. In malignant mesothelioma, there is a very long duration between exposure and the onset of disease, usually greater than 30 years.