Solitary fibrous tumor of the lower urogenital tract: a report of five cases involving the seminal vesicles, urinary bladder, and prostate.

Solitary fibrous tumor (SFT) is not as site-restricted as once believed. Initially described as a tumor of the pleura, SFT is now recognized at various extrathoracic sites. We report 5 cases of extrapleural SFT involving the male lower urogenital tract. The tumors involved the seminal vesicles (2 cases), urinary bladder (2 cases), and the prostate (1 case). The patients with bladder tumors were asymptomatic. The patients with seminal vesicle involvement presented with hematuria or groin pain. The patient with prostate involvement presented with urinary retention. The prostate tumor was large, and it could not be completely excised because of its extensive spread beyond the prostate into the pelvis. The other 4 tumors were completely excised, and none has recurred during limited follow-up. By histological criteria, 4 of the tumors were benign, and 1 was malignant. Even though the classic histological features of SFT were well developed in each case, all 5 tumors were initially misdiagnosed, including 3 benign tumors that were misclassified as sarcomas. These 5 cases confirm the male lower genitourinary tract as yet another site of origin for SFTs, challenge the notion that extrapleural SFTs invariably are benign, and draw attention to the problem of recognizing SFTs when they arise in unexpected sites.