Peritoneal mesothelioma is a rare disease. The tissue lining the abdomen is called the peritoneum. It helps to protect the contents of the abdomen. It also produces a lubricating fluid. This helps the organs to move smoothly inside the abdomen as we move around. Mesothelioma of the tissues lining the abdominal cavity in known as peritoneal mesothelioma.A thin membrane of mesothellial cells, known as the peritoneum develops many of the organs in the abdomen. Peritoneal mesothelioma is a tumor tha.