Retroperitoneal teratoma presenting as an abdominal-pelvic mass.

Nonovarian teratomas are relatively common neoplasms in children, but are rarely seen in adults. A case of a large retroperitoneal teratoma in a 42-year-old woman is presented. The 21.5-kg tumor originated in the retroperitoneal space inferior to the origin of the superior mesenteric artery, and displaced the contents of the entire abdominal cavity. The duodenum, pancreas, and transverse colon mesentery were incorporated into the tumor's pseudocapsule. Evaluation and operative management are described. Diagnosis and pathogenesis of nonovarian teratomas are reviewed.