Mesothelium refers to the outer surfaces of the heart and lungs. This includes the inside of the chest wall and the inside of the bag around the heart called pericardium. In the lung is pleural mesothelium of the pericardium is the heart, and in the abdominal cavity, the name of the peritoneum.

Its main task is to protect these organs by a lubricating fluid, for motion. While mesothelioma can affect the mesothelial tissue in the body that is best in the pleural or peritoneal mesothelium. Unfortunately, many patients are not diagnosed with mesothelioma symptoms are present, and are usually no symptoms until the cancer in its advanced stage.