Immunohistologic diagnosis of 2 cases of metastatic prostate cancer to breast.

We report 2 cases of primary prostatic carcinoma with subsequent carcinomatous lesions in the breast. Prostatic origin of these carcinomas was confirmed by immunocytochemical demonstration of prostatic acid phosphatase and prostate specific antigen within paraffin sections. Previously, only 20 cases of prostatic carcinoma metastatic to the breast have been reported in the literature. In most of these cases the designation of the breast lesion as prostatic carcinoma has been made on morphologic and clinical grounds only.