Abnormal uterine bleeding as a presentation of metastatic breast disease in a patient with advanced breast cancer

Extragenital carcinomas secondarily involving the uterus are very rare and they usually occur as a manifestation of widespread disease. When the metastases involve the endometrium in a diffuse, permeative pattern, sparing the glands, they may cause problems in the diagnosis. A case of metastatic carcinoma to the endometrium with a decidua-like pattern is reported. The patient had a history of breast carcinoma and presented with vaginal bleeding. The pathologic findings in the uterine curettings raised the differential diagnosis between metastatic breast carcinoma and non-neoplastic stromal lesions. The presence of nuclear atypia and mitotic activity along with the appropriate immunohistochemical findings revealed the neoplastic nature of the endometrial lesion and confirmed its origin from the breast. Unusual uterine bleeding in a patient with breast cancer should alert the gynecologist to the possibility of metastatic breast disease. Furthermore, the metastasis to the uterus and to other organs of the genital tract can be considered as a preterminal event.