Solitary fibrous tumor of the prostate.

A case of solitary fibrous tumor of the prostate is reported. A 42-year-old man had been complaining of difficult voiding and constipation for 8 years. Urological and radiological examinations showed a large prostatic mass, and a total cystectomy and prostatectomy were performed. The tumor was 14 x 13 x 11 cm in size, solid with a fibromuscular capsule, and gray-tan in color. Histologically, the tumor was composed of short spindle-shaped and polygonal cells with mild to moderate nuclear atypia, predominantly arranged in the so-called 'patternless pattern' in a fibrocollagenous background. Mitoses were occasionally seen. Vascular invasion was also observed. Immunohistochemically, these cells were strongly positive for CD34 and vimentin, and occasionally for desmin. The maximum Ki-67 labeling index of the tumor cells was 4.5%. These findings are consistent with a solitary fibrous tumor. To our knowledge, this is the first report of a solitary fibrous tumor of the prostate in the English medical literature.