Squamous cell carcinoma of the prostate.

Eleven case of squamous cell carcinoma of the prostate have been divided into four groups according to their histological features and natural history: a pure squamous cell carcinoma of the prostate (one case); b common prostatic adenocarcinoma with malignant squamous component after oestrogen treatment (two); c urothelial carcinoma of the prostate with malignant squamous cell metaplasia (four); and d urothelial carcinoma of the urinary bladder with squamous cell metaplasia growing into the prostate (four). The squamous portions may spread to invade the fibromuscular stroma and grow in prostatic ducts. Necrosis of comedo type and inflammatory infiltrates appeared in a number of cases. The survival times of nine patients ranged from 1 to 17 months. Squamous components were shown by immunohistochemistry to contain various keratin types, carcino-embryonic antigen and peanut agglutinin binding sites. Whenever a squamous cell carcinoma in the prostate is diagnosed histologically various possibilities as to its origin should be considered.