[A case of paraureteral neurilemmoma causing ureteral obstruction: report of a case]

Retroperitoneal neurilemmomas are rare tumors. They are usually asymptomatic, and often become quite large before they are discovered. A case is reported of a 75-year-old man with complaints of general malaise and left lumbar pain. Intravenous pyelography showed left renal nonfunctional and retrograde pyelography revealed the stenosis of the left ureter. The ultrasonogram demonstrated a cystic mass, and it was diagnosed as a retroperitoneal tumor with central necrosis by computerized tomography and magnetic resonance imaging. The tumor was removed with the left nonfunctioning kidney and ureter. The tumor was 3 x 3 x 4 cm, and the histological diagnosis was neurilemmoma (Antoni A + B type). There was a tight fibrous adhesion between the tumor and the left ureter, and the tumor was concluded to have originated from the adventitia of ureter. To date, 120 benign cases have been reported in Japan. They are reviewed and discussed.