What is Mesothelioma?

Mesothelioma is a rare but aggressive form of cancer that starts in the membrane that lines the chest and abdomen (mesothelium). Mesothelioma most commonly forms in the lung pleura (~75% of all cases), which is the set of membrane (pleura) around the lungs. Mesothelioma may also form in the peritoneum, which is the membrane around the abdomen, or the pericardium, which is the membrane around the heart. Peritoneal mesothelioma accounts for about 10% to 20% of all cases, and pericardial mesothelioma accounts for about 1% of all cases.

Mesotheliomas are also classified based on the types of cells in which they form. Epithelioid mesotheliomas form in round, cube-like epithelial cells and account for about 60% to 70% of all cases. Sarcomatoid mesotheliomas form in spindle-shaped cells and account for about 10% to 20% of all cases. Biphasic mesotheliomas have characteristics of both epithelioid and sarcomatoid mesotheliomas and account for about 10% to 15% of all cases. Sarcomatoid and biphasic mesotheliomas are typically more aggressive in their behavior than the epithelioid subtype.