[A Case of Retroperitoneal Teratoma Difficult to Distinguish from Adrenal Tumor].

Retroperitoneal tumor is a rare tumor, with an incidence of 0.2 to 0.8%. Among such tumors, the frequency of teratomas ranges from 6 to 18%, and adult cases are extremely rare. We report a mature teratoma that occurred in the retroperitoneum of 43-year-old woman. She experienced back pain and a left adrenal gland mass was detected on computed tomography. Computed tomography and magnetic resonance imaging findings showed a cyst made of fat and calcification, but it was difficult to distinguish retroperitoneal teratoma from adrenal tumor in this case. The tumor was removed, and was mainly composed of a hair ball and fat. Pathological examination showed that the tumor was composed of stratified squamous epithelium, keratinizing component, cartilage, and bronchial epithelium, while no continuity with the adrenal gland was observed. Therefore, the tumor was diagnosed as a retroperitoneal teratoma.