Metastatic breast carcinoma to the ovary is sometimes difficult to differentiate from primary ovarian carcinoma. This problem is often encountered in breast carcinoma patients who develop adnexal masses. ER and PR can be positive in a high percentage of breast and ovarian carcinomas, and therefore cannot be used in the differential diagnosis of these entities. WT1 and CA125 have been identified as possible markers for ovarian cancer. However, no studies have been done that specifically compare the immunophenotype of breast carcinoma metastatic to ovary with that of primary ovarian cancer. Thirty-nine cases of metastatic breast carcinoma to the ovary, 36 primary breast carcinomas, and 42 primary ovarian carcinomas were examined immunohistochemically for the expression of WT1, CA125, carcinoembryonic antigen, MUC2, MUC1, and GCDFP. The percentage of cells stained and the intensity of staining were recorded. Thirty-two ovarian carcinomas (76%) were positive for WT1, including 31 of 33 (94%) serous carcinomas. Most of them had strong and diffuse staining. None of the breast cancers either primary or metastatic to the ovary expressed WT1. Thirty-eight (90%) ovarian carcinomas were positive for CA125, most of them with strong and diffuse staining. Most breast carcinomas were negative for CA125, with only 6 (16%) of the primary ones and 5 (12%) of the metastatic showing weak and focal positivity. All ovarian carcinomas were negative for GCDFP. Five primary breast cancers (14%) and 17 (43%) metastatic to the ovary were positive for GCDFP. Nine (21%) ovarian carcinomas, 8 (22%) primary breast carcinomas, and 13 (33%) metastatic to the ovary were positive for carcinoembryonic antigen. Almost all tumors examined were positive for MUC1 (100% ovarian carcinomas, 100% primary breast carcinomas, and 95% metastatic breast carcinomas to ovary). MUC2 was positive in 10 (24%) ovarian carcinomas, 3 (8%) primary breast cancers, and 12 (30%) metastases to the ovary. The presence of immunoreactivity for WT1 and CA125 in a carcinoma involving ovary strongly favors a primary lesion. Most ovarian carcinomas are positive for both markers, whereas the majority of metastatic breast carcinomas to the ovary are negative. GCDFP can be complementary in this differential diagnosis.

Stage I, low-grade endometrioid and mucinous ovarian carcinomas have an excellent prognosis. Published data have suggested that destructive stromal invasion, a relatively uncommon finding in these tumors, is a poor prognostic factor. We investigated this by studying all FIGO stage I, grades 1 and 2 (of 3) endometrioid and mucinous ovarian carcinomas that were surgically staged at the Memorial Sloan-Kettering Cancer Center from 1980 to 2000. We undertook a careful review of all available slides using current diagnostic criteria and correlated histopathologic indices with clinical outcome data. Cases studied included 13 endometrioid ovarian carcinomas (stage IA, eight; stage IC, five) and six intestinal mucinous ovarian carcinomas (stage IA, three; stage IC, three). All of the tumors contained areas of expansile invasion, greater than that acceptable for microinvasion, and were thus diagnosed as carcinomas instead of borderline tumors. Nevertheless, nearly all demonstrated borderline tumor (noninvasive) components. Six tumors contained at least one focus of destructive stromal invasion (two endometrioid and four mucinous ovarian carcinomas). Four additional cases showed a focus suspicious for but not diagnostic of destructive invasion ('indeterminate for destructive invasion') (two endometrioid and two mucinous ovarian carcinomas). Follow-up data were available for 17 patients. The median follow-up was 81 months (range, 9-161 months). In all, 14 patients were alive with no evidence of disease (expansile invasion alone, eight; destructive stromal invasion, four; and indeterminate for destructive invasion, two). Three patients died of their disease (destructive stromal invasion, two; and indeterminate for destructive invasion, one). The size, number, and nuclear grade of destructive stromal invasion foci did not appear to have an impact on survival in this relatively limited number of patients. Outcome data in patients with stage I, low-grade endometrioid and mucinous ovarian carcinomas without destructive stromal invasion indicate that these tumors have a very limited malignant potential. The literature has not documented recurrences in this setting when the staging has been complete, the sampling adequate, and the cytologic features no more than grade 2, and metastasis to the ovary has been excluded. In contrast, carcinomas harboring even limited foci of destructive stromal invasion, although frequently cured surgically, can pursue a malignant clinical course. Modern Pathology (2005) 18, 903-911.