Growing teratoma syndrome after chemotherapy for a mixed germ cell tumor of the ovary.

A retroperitoneal enlarging mass was detected and resected in a 24-year-old nulliparous woman after fertility-preserving surgery and adjuvant chemotherapy for a malignant germ cell tumor (MGCT) of the right ovary. This enlarging mass contained only a mature teratoma component. Alpha-fetoprotein, which was elevated to 21236.6 ng/mL before the initial surgery, persisted within normal after the completion of adjuvant platinum-based chemotherapy. The patient was diagnosed with growing teratoma syndrome. Growing teratoma syndrome originating from ovarian germ cell tumor is very rare. Only 15 cases have been reported. Surgical resection and histological confirmation of growing mass after MGCT treatment is essential before conducting salvage chemotherapy.