The National Cancer Institute defines malignant mesothelioma as a rare form of cancer and a disease in which cancer cells are found in the sac lining the chest called the pleura, the lining of the abdominal cavity called the peritoneum or the lining around the heart called the pericardium.

One of the most common symptoms of mesothelioma is pleural effusions. Pleural effusions are an accumulation of fluid between the lining of the lung and the chest cavity. This sign of mesothelioma is noticed as the fluid increases and the ability to breathe decrease. Pain and or discomfort while breathing can accompany the shortness of breath. The proper diagnosis can be given by a doctor through the use of x-rays and CT scans.