Primary peritoneal cancer or carcinoma is also known as serous surface papillary carcinoma, primary peritoneal carcinoma, extra-ovarian serous carcinoma, primary serous papillary carcinoma, and psammomacarcinoma. It was historically classified under "carcinoma of unknown primary" (CUP). Primary peritoneal cancer (PPC, or PPCa) is a cancer of the cells lining the peritoneum, or abdominal cavity. It usually affects women and is diagnosed after the age of 60; it very rarely affects men. Histomorphological and molecular biological characteristics suggest that serous carcinomas, which include ovarian serous carcinoma, uterine serous carcinoma, fallopian tube serous carcinoma, cervical serous carcinoma, and primary peritoneal serous carcinoma really represent one entity.

Reference
Wiki: Ovarian serous carcinoma