Malignant peritoneal mesothelioma is an extremely rare cancer. Only 100 to 500 cases are diagnosed in the US each year, making up less than 30% of all mesothelioma cases.
Peritoneal mesothelioma is a cancer affecting the abdominal lining, or peritoneum (paira-tin-e-um), which is why is is sometimes referred to as abdominal mesothelioma. This membrane supports and covers the organs of the abdomen.
The peritoneum is made of two parts, the visceral and parietal peritoneum. The visceral peritoneum covers the internal organs and makes up most of the outer layer of the intestinal tract. Covering the abdominal cavity is the parietal peritoneum.
Cells in these linings secrete a fluid which allows organs to move against one another. For instance, as the intestines move food through the body. The cells of the mesothelium are designed to create fluid, but the cancer can cause them to overproduce, creating a build up of excess fluid in the abdominal cavity.