Malignant transformation of a mature retroperitoneal teratoma into adenocarcinoma

Retroperitoneal mature teratoma is a rare congenital tumor, far behind ovarian and testicular localizations. Malignant transformation of teratomas is extremely uncommon. We report a case of a 23-year-old female, who presented with chronic pelvic heaviness, abdominopelvic ultrasound revealed a cystic mass in the right iliac fossa, initially considered as a functional ovarian cyst. Given the persistence of the patient's symptoms a pelvic MRI was requested. It showed a right retro-colic cystic unilocular with parietal nodule. The two ovaries showed normal appearance. A retroperitoneal teratoma was suggested given the retroperitoneal topography of the mass, and the presence of a tissular parietal nodule. She underwent surgery and the diagnosis was confirmed after histological study