Adenosquamous carcinoma of the prostate.

An unusual adenosquamous carcinoma originating in the prostate of a 70-year-old man is described. Four years prior to the development of this lesion, a diagnosis of adenocarcinoma had been established by needle biopsy and the patient had been treated with radiation. Light microscopic examination revealed a pattern of adenocarcinoma predominant in the periurethral region and squamous cell carcinoma at the periphery. The latter neoplastic component involved the bladder and rectum and extended to the pelvic wall. Immunoperoxidase staining for prostatic acid phosphatase occurred in both cellular components, and electron microscopic examination confirmed the squamous differentiation of tumor cells.