RESUMEN
An 82-year old man received total androgen blockade therapy (bilateral orchiectomy and 375 mg/day flutamide) for the treatment of stage C prostate cancer. Serum PSA levels were undetectable for 13 months and thereafter increased gradually. We administered estramustine phosphate sodium (EPS) instead of flutamide under the diagnosis of hormone refractory prostate cancer. EPS therapy was discontinued after 9 months because serum PSA levels increased again. Then, the patient complained of bilateral breast nodules and pain. Bilateral mammectomies were performed due to bilateral breast cancers which had been diagnosed by aspiration biopsies and radiographic examinations, but he died four months after the operations. Final pathological diagnosis was ductal adenocarcinoma of the breasts. Immunohistochemical study revealed expressions of PSA in the breast cancers. We diagnosed double cancers of the prostate and the breast because of the different expression patterns of progesterone receptor between them. We review the literatures and discuss the differential diagnosis of prostate cancer and PSA-producing breast cancer.