Retroperitoneal mucinous cystadenoma.

A case of retroperitoneal mucinous cystadenoma histologically confirmed in a 21-year-old woman is reported. Although ultrasound, CT and MR detected the tumor, a preoperative diagnosis could not be established by imaging methods. The cystic tumor was removed and microscopic examination revealed a mucinous cystadenoma. Mullerian mesothelial metaplasia of peritoneal invagination into the retroperitoneal space is the most likely explanation for the histogenesis of these tumors.