Cancer spreading in the peritoneum, known as peritoneal carcinomatosis or peritoneal metastases, is the general term for spreading of tumor cells in the peritoneum often originating from other organs in the abdominal cavity. Spread may also occur when a tumor grows through an organ reaching the surface of the peritoneum. Free cancer cells can implant into different areas of the peritoneum.
The peritoneum is a thin membrane consisting of two layers:
- a peritoneal layer which lines the abdominal cavity
- a visceral layer which wraps around the internal organs in the intraperitoneal cavity
The narrow space between these two layers is filled with a thin fluid keeping the peritoneum moist to allow the two layers to glide freely. Double layer of peritoneum is known as mesentery which houses organs.
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 peritonei (PMP) is a malignant condition in the appendix characterized by mucinous ascites and peritoneal, mucinous implantations. Mesothelioma is tumor originating from mesothelial cells that lines body cavities.The most common origin is the pleural cavity, but tumor may also originate from the peritoneal cavity.
About 5-8 % of patients with primary colon cancer and 2% of patients with rectal cancer have carcinomatosis at the time of diagnosis. Several patients have peritoneal metastases at the time of recurrence. In about half of patients with peritoneal carcinomatosis, there is also distant metastases, which makes it complicated to cure the disease.
There are about 20 new cases of pseudomyxoma peritonei per year in Norway. (3-4/million/year). Diffuse malignant peritoneal mesothelioma (DMPM) makes up 1/4 of all mesothelioma.