Malignant mesothelioma is a type of cancer that grows on the mesothelium, which is the lining of the organs in the body. It’s most often found in the lungs, resulting in pleural mesothelioma. However, you can also get peritoneal mesothelioma in the abdomen or pericardial mesothelioma in the heart tissue. Testicular mesothelioma is another form of this condition, though it’s much more rare than pleural mesothelioma. Regardless of the type of mesothelioma you were diagnosed with, it was likely caused by long-term exposure to asbestos products.