Mesothelioma is a rare type of cancer that that develops in the pleura, a thin membrane that separates the lung from the chest wall. It usually occurs from prior exposure to asbestos, a type of mineral fiber used in the insulation industry., Mesothelioma is a rare cancer that most commonly starts in the lining around your lungs. It can also start in the lining or sac around your abdomen, heart or testicles. Symptoms include shortness of breath, cough, night sweats, chest pain and digestive issues., In stage IV, cancer has spread to the tissue covering the lung or the lung on the opposite side of the chest, peritoneum, bones, liver, lymph nodes outside the chest, or to other parts of the body. Stage IV malignant mesothelioma is also called metastatic mesothelioma., , , .