Incidence of serous tubal intraepithelial carcinoma (STIC) by algorithm classification in serous ovarian tumor associated with PAX8 expression in tubal epithelia: a study of single institution in Japan.

Serous ovarian carcinoma is now hypothesized to originate from fallopian tube epithelium (FTE). We investigated the FTE abnormalities in the patients with epithelial ovarian tumors. Our study included 55 cases of serous tumors (24 carcinomas, 8 borderline tumors, and 23 adenomas), 14 mucinous carcinomas, 22 endometrioid carcinomas, 5 clear cell carcinomas, and 2 malignant Brenner tumors. FTE was diagnosed by the diagnostic algorithm, which combines the data of morphology, and p53, Ki-67 immunostaining, as serous tubal intraepithelial carcinoma, serous tubal intraepithelial lesion, p53 signature, and normal/reactive. Serous tubal intraepithelial carcinoma, serous tubal intraepithelial lesion, p53 signature, and normal/reactive were observed in 5, 3, 0, and 16 cases in serous carcinoma; 0, 3, 0, and 5 cases in serous borderline tumor; 0, 1, 1, and 21 cases in serous adenoma; 0, 0, 1, and 13 cases in mucinous carcinoma; 0, 0, 3, and 19 cases in endometrioid carcinoma; 0, 0, 0, and 5 cases in clear cell carcinoma; and 0, 1, 0, and 1 case in malignant Brenner tumor. Among tumors of serous histology and between carcinomas, FTE abnormalities differed significantly (P<0.05). Serous tubal intraepithelial carcinomas were only found in serous carcinoma. The incidence of secretory cell proliferation (SCP) was examined by PAX8 expression. The rate of SCP was extremely high in serous carcinoma (96%). Among tumors of serous histology and between carcinomas, an incidence of SCP differed significantly (P<0.05). Patients with SCP were significantly older (P<0.0001). Our observations were concordant with the hypothesis of serous ovarian carcinogenesis. The SCP has a meaningful association with serous ovarian cancer.