Malignant peritoneal mesothelioma is a cancer of the peritoneum, or tissue lining the abdomen and some of its organs. This lining tissue provides a small amount of lubricating fluid that allows organs in the gut to move and work properly. This cancer accounts for approximately ten percent of all malignant mesotheliomas and is therefore rarer than malignant pleural mesothelioma, which affects the tissue lining the chest and lungs. Irrespective of location, the majority of malignant mesotheliomas are associated with exposure to asbestos.

A person with malignant peritoneal mesothelioma may be diagnosed because of complaints such as an abdominal lump or swelling, unexplained weight loss, fever, loss of appetite, abdominal pain, nausea, and constipation caused by bowel obstruction. There are many other conditions that could cause similar symptoms, and in the absence of an accurate history of asbestos exposure, a diagnosis of malignant peritoneal mesothelioma may be missed.

When malignant peritoneal mesothelioma is suspected, the patients doctor orders a CT scan or an MRI to detect the presence of any abnormality in the abdomen. If features suggesting this cancer are present, a biopsy of the potentially cancerous tissue is taken to determine the types of cells in this tissue.

Once diagnosed, the exact treatment and the eventual outcome depend on the types of cells found in the cancer. People with epithelioid cell cancers typically have the best survival, followed by those with mixed cell cancers. Sarcomatoid cell cancers carry the worst prognosis. The average survival time is approximately one year, and five-year survival is lower than ten percent. Because of this poor prognosis, the cancer is treated as aggressively as the patients overall physical condition allows, with some combination of surgery, radiotherapy and chemotherapy. Surgery helps remove the bulk of the cancer. Radiotherapy and chemotherapy are then used to kill the remaining cancer cells.