Pelvic confined idiopathic retroperitoneal fibrosis mimicking a large tumor

Idiopathic retroperitoneal fibrosis (IRF) entirely confined to the pelvic cavity is an extremely rare clinical entity. Herein, is described the case of a 36- year old male who presented with clinical and imaging manifestations of a large pelvic tumor. Exploratory laparotomy revealed a large mass in the right pelvis originating from the retroperitoneal space, displacing the right iliac vessels, the right ureter and the urinary bladder completely to the left. A laborious resection of the mass measuring 14 x 10cm was performed. Histopathological examination and detailed immunohistochemistry analysis were suggestive of idiopathic retroperitoneal fibrosis with no evidence of malignancy. This is a very rare case regarding localization and clinical presentation of idiopathic retroperitoneal fibrosis. We conclude that IRF should be included in the differential diagnosis of patients presenting with a pelvic mass even if there is no involvement of the typical para aortic area.