Retroperitoneal Castleman's disease presenting with hydronephrosis indistinguishable from lymphoma

Castleman's disease is a rare benign lymphoproliferative disease. We describe a patient with an unusual case of retroperitoneal Castleman's disease who initially presented with hydronephrosis. Her disease manifested with a malignant appearance in positron emission tomography/computed tomography and was located in the common and internal iliac area. Retrograde double-J stent insertion failed and nephrostomy was then performed. Complete surgical removal of the disease failed because the disease was severely adherent to the ureter and adjacent iliac vessels. Antegrade double-J stent insertion also failed. The patient eventually underwent laparoscopic ureteroneocystostomy. Retroperitoneal Castleman's disease should be added to the extensive list of differential diagnoses for primary retroperitoneal tumors.