Metastatic prostatic adenocarcinoma within a primary solid papillary carcinoma of the male breast.

We report the case of a 78-year-old man who developed a breast mass 12 months after hormonal therapy for palliation of prostatic adenocarcinoma. On histologic and immunohistochemical examination, the breast tumor revealed a unique collision tumor composed of metastatic prostatic adenocarcinoma and solid papillary breast carcinoma.