Clinicopathologic Review of Metastatic Breast Cancer to the Gynecologic Tract.

Metastatic spread is the single most significant predictor of poor survival in breast cancer. Some of the most common metastatic sites are the bones, lungs, liver, brain, and peritoneal cavity. Clinically metastatic breast cancer to the gynecologic tract is usually asymptomatic and diagnosed as an incidental finding during a histologic examination of gynecologic specimens resected for other reasons. Cases of metastatic breast cancer to gynecologic organs diagnosed from August 1995 to January 2021 were retrieved from our institution's pathology databases, and their clinicopathologic features were reviewed. The most common site of metastasis was the ovary which was involved in about 79% (22 of 28 cases) of metastases to the gynecologic tract. Clinically, only 8 cases (36%) presented with ovarian mass detected in imaging studies and the rest of the cases were all incidental findings. Among ovarian metastasis, 59% of cases were invasive lobular carcinoma and 41% were invasive ductal carcinoma. In 5 cases, metastatic breast cancer was found in the endometrium, including 2 cases with endometrial metastasis only and 3 cases with multiple gynecologic organs involved. Metastatic breast cancer rarely involved the lower gynecologic tract, with only 7% vaginal metastasis and 4% found in the vulva. The absolute majority of metastatic breast cancer outside of the ovaries were lobular carcinoma (88%). Most of the metastatic breast carcinomas were positive for estrogen receptor on immunohistochemistry (27 of 28 cases, 96%). Her-2/neu immunostaining was positive in 4 cases only (14%). Metastatic breast cancer needs to be distinguished from gynecologic primary neoplasms and metastatic tumors from adjacent urinary and GI tracts. A careful review of the patient's history and adequate immunohistochemistry panel are helpful to render the diagnosis.