Mesothelioma is a type of cancer that can develop in the tissues covering the lungs or the abdomen. It is a cancer of mesothelial cells. These cells cover the outer surface of most of our internal body organs, forming a lining that is called the mesothelium.

Mesothelioma in the chest

About three quarters of mesotheliomas occur in the chest (75%). They start in the two sheets of tissue known as pleural membranes (or pleura) that cover the lungs. The gap between the pleura is called the pleural space. The pleura are fibrous sheets that help to protect the lungs. They also produce a lubricating fluid that helps the pleural membranes to slide over each other easily when the lungs expand and deflate as we breathe. Mesothelioma of the pleura is called pleural mesothelioma.

The sheet of tissue covering the heart (the pericardium) is very close to the pleura. So in some people pleural mesothelioma may also spread into the pericardium. The diagram below shows the pleural membranes thickening due to mesothelioma.

Mesothelioma in the abdomen

The sheet of tissue covering the organs of the abdomen (tummy) is called the peritoneum. It helps to protect the contents of the abdomen and keep them in place. It also produces a lubricating fluid. The fluid helps the abdominal organs to move smoothly against each other as we move around.

Mesothelioma of the tissues lining the abdominal cavity is known as peritoneal mesothelioma About a quarter of mesotheliomas occur in the abdomen (25%). So it is much less common than pleural mesothelioma. Peritoneal mesothelioma does not usually spread to other parts of the body

Benign mesothelioma

A type of non cancerous (benign) mesothelioma can develop in the lining of the lungs, or in the lining of the reproductive organs. It can occur in either men or women. These non cancerous tumours are very rare and we don't cover them in this section.