“Primary peritoneal” high-grade serous carcinoma is very likely metastatic from serous tubal intraepithelial carcinoma: Assessing the new paradigm of ovarian and pelvic serous carcinogenesis and its implications for screening for ovarian cancer

ObjectivePrimary peritoneal high-grade serous carcinoma is thought to arise from the peritoneum, but recent data suggest that the fallopian tube may be an occult source of many of these tumors. This study was performed to evaluate this hypothesis in an unselected series of cases.MethodsFallopian tubes from 51 consecutive cases meeting the GOG criteria for primary peritoneal high-grade serous carcinoma, FIGO stages II–IV, were analyzed.ResultsSerous tubal intraepithelial carcinoma (STIC) was identified in 19 patients (37%). When the fimbriae were examined, STIC was identified in 46%, and when all tubal tissue was examined, 56%. STIC was confined to the fimbriae in 53%, involved fimbriae and nonfimbrial mucosa in 20%, and was confined to nonfimbrial mucosa in 20%. Patients with STIC were significantly older than those without STIC (75 years vs. 67 years, respectively; p = 0.007). Patients with STIC were significantly more likely to have FIGO stage IV disease as compared to those without STIC (42% vs. 12.5%, respectively; p = 0.037).ConclusionsAt least half the cases of primary peritoneal high-grade serous carcinoma are associated with intraepithelial carcinoma of the fallopian tube, usually involving the fimbriae. These findings support the view that, like “primary ovarian carcinoma,” what has been traditionally classified as “primary peritoneal carcinoma” is probably derived from occult high-grade serous carcinoma in the fallopian tube. These findings have important implications for ultrasound screening trials for ovarian cancer which are based on the assumption that an enlarged ovary is a very early manifestation of disease.

Research highlights
► Tubal intraepithelial carcinoma is seen in 37% of women with peritoneal carcinoma.
► The tubal fimbrial mucosa may be the site of origin of “peritoneal” serous carcinoma.
► Findings support the new paradigm indicating tubal origin of pelvic serous carcinoma.