Primary Peritoneal Carcinoma Can Have Multifocal Origins: Implications for Prophylactic Oophorectomy

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Abstract
The clinical entity of primary peritoneal carcinoma has had many different names, including papillary serous carcinoma of the peritoneum (PSCP). First reported in 1959 (1), PSCP refers to the diffuse involvement of peritoneal surfaces with a neoplasm appearing identical to papillary serous carcinoma of the ovary, in the absence of a demonstrable primary ovarian tumor. It can occur in women after oophorectomy for prophylaxis or benign disease or in women with intact ovaries. Clinically, it is indistinguishable from stage III epithelial ovarian cancer (2,3). Historically, there have been two theories about the origin of this cancer. The first is that the tumor develops in the ovarian surface epithelium and subsequently spreads throughout the peritoneal cavity. The primary tumor is postulated to be microscopic, and therefore not detectable, or to have regressed completely. The second theory is that the disease starts de novo in the peritoneal mesothelium, which is of müllerian origin. This theory seems plausible because the cell of origin of epithelial ovarian cancer is the peritoneal reflection on the surface of the ovary, not the underlying stromal or germ cell components. PSCP may be particularly relevant in women with inherited susceptibility to ovarian cancer, where germline mutations create a field defect. In this setting, the entire peritoneal surface, not just that covering the ovary, is at risk for malignant transformation. However, the peritoneal reflection on the surface of the ovary may be particularly vulnerable to malignant transformation as a result of repeated injury following ovulation andhigh levels of local estrogen exposure.