ABSTRACT
Through a routine antenatal ultrasound examination of 37-year-old woman at 38 weeks' gestation, a 6 cm-diameter mixed solid and cystic mass was found in the left suprarenal area of her fetus. The following antenatal magnetic resonance image showed a larger cystic mass with a central solid component. The surgical exploration of the mass was performed in 50 days after delivery and by the pathologic examination a grade III immature teratoma was found. The retroperitoneal immature teratomas are extremely rare in childhood. To our Knowledge this is the first reported case about congenital retroperitoneal immature teratoma. The immature teratoma should be included in the differential diagnosis of fetal suprarenal mass and the serum alpha-fetoprotein level should be included in the initial laboratory examination at birth.