[Pelvic fibromatosis simulating urachal tumor--a case report].

We report a case of pelvic fibromatosis, which has been rarely found. A 36-year-old man referred to our hospital complaining of right abdominal pain and a swelling mass. Abdominal CT and transabdominal echogram revealed a tumor contacted to the bladder. A nonpapillary tumor (little finger sized) at the bladder dome was observed by cystoscopy, and the tumor was clinically considered as urachal tumor. Wide radical excision including the bladder and prostate was performed. Pathological diagnosis was pelvic fibromatosis arising from musculoaponeurotic structures in the pelvis: The fibromatosis is benign nonmetastatic tumor but the recurrence rate is considerably high. However, in the present case, 14 months after operation there is no recurrence yet.