What is Mesothelioma?

Mesothelioma is a cancer of the mesothelium; the protective sac that covers and protects most internal organs of the body. The mesothelium has two layers, one, which covers the organ, and a second, which forms a sac around it. The mesothelium has different names depending on the location in the body. The pleura is the name for the mesothelial tissue surrounding the lungs and lining the chest cavity. The peritoneum covers most of the organs in the abdominal cavity, while the pericardium covers and protects the heart.