Malignant B-cell lymphoma in renal cyst wall.

Renal cysts are frequently found in adults older than 50 years of age. Bosniak type III and IV cysts are commonly associated with malignancy, but most Bosniak I and II lesions are benign, and the optimal management has not been clearly defined. Although computed tomography and ultrasound examinations have improved diagnostic accuracy, some masses will remain indeterminate and require more invasive evaluation. We report a patient with a Bosniak type II renal cyst associated with malignant B-cell lymphoma in the cyst wall diagnosed after laparoscopic renal exploration.