[Solitary fibrous tumor of the urinary bladder: a case report].

Solitary fibrous tumor (SFT) is one of the mesenchymal tumor usually occurs in the pleura. Extrapleural occurrence of SFT is uncommon. We herein report an extremely rare case of 72-year old man with SFT originated in the urinary bladder. The tumor was incidentally discovered as a mass of 8.5 mm in diameter by a pelvic MRI. Cystoscopy revealed the protruding submucosal tumor in the center of the trigon. Transurethral resection was carried out. Pathological examination revealed a tumor composed of spindle cells with rich vascularity surrounded by abundant collagen fibers. The immunohistochemical findings showed a strong positivity to CD 34 and relatively weak positivity to Bcl-2. MIB-1 index indicated less than 3%, thus the tumor was diagnosed as a solitary fibrous tumor. The patient has no evidence of disease 16 months after the surgery. The current case was the first report in Japan and the twelfth worldwide.