Primal and secondary (metastatic) tumors of the peritoneum
Rare cancers.
Primary peritoneal tumours
The most common form is mesotheliomas, a malignancy of mesothelial cells that arises from the lining surfaces of the peritoneal cavity. Has significant male predominance, and a history of asbestos exposure.
Grossly, we see hard whitish nodules scattered over the peritoneal surface, these nodules coalesce into plaques. Microscopically, we see extensive vacuolization, psammoma bodies and the presence of hyaluronic acid without mucin.
A second type of peritoneal cancer is the Extraovarian primary peritoneal carcinoma. Histopathologically similar to ovarian cancer, EOPPC is commonly a serous surface carcinoma.
Secondary
- Metastasis can come from breast and lung
- Spread via direct invasion, lymphatic paths, intraperitoneal seeding and hematogenous spread
- Pseudomyxoma peritonei is form of secondary tumour that occurs due to the rupture of a cystadenocarcinoma of the appendix or colon seeding carcinogenic cells in the peritoneal surface
Example: secondary tumours are far commoner than primary ones. The usual sources of peritoneal carcinomatosis are carcinomas of the ovary, stomach, colon and pancreas: e.g. a patient with gastric signet-ring cell carcinoma develops ascites containing tumour cells and a thick, tumour-filled omentum (“omental cake”).