Castleman's disease of the mesorectum: report of a case.

Castleman's disease is a benign lymphoid proliferative disorder, which most commonly presents as a solitary mass in the mediastinum, although extrathoracic sites have been reported in the neck, axilla, pelvis, mesentery, pancreas, and retroperitoneum. We report a case of asymptomatic, isolated Castleman's disease in the mesorectum, which is extremely rare. The patient was a 34-year-old woman who underwent investigations for vaginal spotting. A presacral mass was located on the left side of the rectum, 10 cm from the anal verge. Contrast-enhanced computed tomography showed a large, well-demarcated, strongly enhancing mass with internal radiating septa in the mesorectum. The mass was well circumscribed and isointense to muscle on T1-weighted magnetic resonance imaging, appearing as a slightly hyperintense mass on T2-weighted imaging. We performed laparoscopic mesorectal mass excision, and histological examination revealed features typical of the hyaline-vascular type of Castleman's disease. Thus, when a mesorectal mass is being investigated, Castleman's disease should be considered in the differential diagnosis.