Metastasis from breast lobular carcinoma to an endometrial polyp. Report of a case with immunohistochemical study.

A case of lobular carcinoma of the breast metastatic to an endometrial polyp is described. The patient underwent a simple mastectomy and axillary lymphadenectomy because of infiltrating lobular carcinoma diagnosed three years before. Abdominal ultrasound revealed an endometrial polyp. An endometrial biopsy was performed but only scanty material insufficient for diagnosis was obtained. A total hysterectomy and bilateral salpingo-oophorectomy was made. The uterus contained a large polyp which microscopically showed sheets and ribbons of small atypical cells infiltrating the stroma. Immunohistochemical stains were positive for epithelial cell markers. To our knowledge this is the first case of an infiltrating lobular carcinoma metastasizing to an endometrial polyp.