Mesothelioma is a very rare form of lung cancer that arises in the mesothelium. The mesothelium is made up of parietal and visceral membranes, thin layers of tissue, which surround organs and body cavities, such as the lungs or abdomen. The visceral membrane immediately surrounds the organ, and the parietal membrane is a sac covering the visceral membrane. The visceral and parietal membranes that make up the mesothelium. This fluid helps organs move easily among surrounding structures. In the case of the lung, it helps reduce friction between the lung and chest wall during normal breathing as the lung expands.
The mesothelioma is referred to by different names, depending on what part of the body it is found in. In the abdomen, it is called the peritoneum, in the lungs, the pleura, and in the heart, the pericardium. These correspond to peritoneum mesothelioma (cancer of the abdomen/stomach), pleural mesothelioma (cancer of the lung lining) and pericardium mesothelioma.