Peritoneal surface malignancy, commonly known as peritoneal carcinomatosis, is cancer within the peritoneal cavity. The peritoneal cavity is the space between the organs in the abdomen and is lined by the peritoneum, which is normally a thin protective membrane. Cancer of the peritoneum is often caused by the spread of cancer cells from pre-existing cancer.

The peritoneum is a very complex membrane. It has an outer layer called the parietal peritoneum that is attached to the abdominal and pelvic walls. It also has an inner layer – the visceral peritoneum – that is wrapped around some of the abdominal organs. The space between these two layers is called the peritoneal cavity. It is filled with a fluid that lubricates the layers and allows them to slide past each other. Unfortunately, this fluid also allows cancers in the peritoneum to easily spread along the membrane’s large surface area.

Where do peritoneal tumors originate?

Every year, many patients worldwide are confronted with a diagnosis of “peritoneal cancer”.

This includes patients with rare diseases such as malignant mesothelioma and Pseudomyxoma peritoneal (PMP).

More often, peritoneal cancer arises from metastases from a cancer elsewhere in the body.

The most common point of origin for peritoneal cancer is the appendix and the colon for both males and females, as well as the gynecologic organs in women.

However, any tumors in the abdominal cavity can cause peritoneal carcinomatosis. Pseudomyxoma peritoneal (PMP) is a malignant condition in the appendix characterized by mucinous ascites and peritoneal, mucinous implantations.

Mesothelioma is tumor originating from mesothelium cells that lines body cavities. The most common origin is the pleural cavity, but tumor may also originate from the peritoneal cavity.

Often, a recurrence of an abdominal cancer will present as a peritoneal cancer.

In rare cases (fewer than 7 cases per 1 million people each year), a cancer will start in the peritoneum. These tumors include primary peritoneal serous carcinoma (PPSC) and peritoneal mesothelioma. Diagnosis of a primary tumor in the peritoneum can be difficult; primary peritoneal tumors are sometimes misdiagnosed as adenocarcinomas of unknown primary.

An experienced pathology team can perform the extensive workup with immunomarkers necessary for arriving at the correct diagnosis.