Growing teratoma syndrome arising from malignant mixed germ cell tumor: Case report and review of literature

• Growing teratoma syndrome is a rare phenomenon observed in the treatment of germ cell tumors. • Tumor tissue affected by Growing teratoma syndrome consists of mature teratoma. • Cases containing a teratoma component often develop growing teratoma syndrome. • Preoperative elevation of alpha-fetoprotein may be associated with the development of growing teratoma syndrome. Growing teratoma syndrome (GTS) is a condition in which tumor markers normalize during chemoradiation of germ cell tumors, but metastatic or recurrent lesions increase, and the lesions are histopathologically composed of mature teratomas. The incidence of GTS among intracranial germ cell tumors is estimated to be 5 %, making it a relatively rare condition. Here, we describe the case of an 8-year-old female with GTS 1.5 months after initial surgery. A suprasellar tumor was identified, and an endoscopic biopsy was performed. It was a mixed germ cell tumor, consisting mainly of immature teratomas, germinomas, and choriocarcinomas. After chemotherapy, both alpha-fetoprotein (AFP) and beta human chorionic gonadotropin decreased, but the suprasellar tumor grew rapidly and hydrocephalus developed. A craniotomy was performed, and the tumor was completely removed. Histopathological examination revealed that the tumor was a mature teratoma. A teratoma component has been identified in most biopsy specimens of mixed germ cell tumors that produce GTS. However, in some cases, GTS occurred even when teratomas were not detected in the biopsy specimens. As biopsies do not reflect the entire tumor histology, it is important to consider the possibility of conversion to GTS in cases of elevated AFP levels or imaging findings suspicious for teratoma, even in cases where the specimen does not contain a teratoma.