Pitfall in renal cyst surgery: serous cystadenoma of pancreas mimicking renal cyst.

Pancreatic lesions, particularly cysts, can simulate various diseases. We report a case of a 43-year-old woman with a large, symptomatic, retroperitoneal cyst misdiagnosed as a "renal cyst." During the retroperitoneoscopic marsupialization, the correct diagnosis of a pancreatic cyst was made, leading to an open pancreas tail resection. Histologic evaluation revealed serous cystadenoma. Especially in large retroperitoneal cysts on the left side, the correct diagnosis of a pancreatic cyst can be difficult.