Intracranial growing teratoma syndrome observed at 44 months after initial treatment; a case presentation and literature review.

Intracranial growing teratoma syndrome (iGTS) is rare phenomenon which is observed in non-germinomatous germ cell tumor (NGGCT) after chemotherapy. The clinical features of iGTS are rapidly increasing in size compared with relapse, no elevation of tumor marker in spite of tumor regrowth, multiple cystic lesions in cranial imaging, and histopathologically diagnosed as mature teratoma. Here we present a 14-year-old man with iGTS which was revealed at 44 months after initial chemotherapy. He was diagnosed as pineal immature teratoma by histopathological specimen, and we performed chemotherapy and radiation therapy. After this treatment, we found growing cystic lesion in tumor removal cavity at 26 months after surgery. The histopathological findings showed dermoid cyst in first salvage surgery. Following this result, we observed him without adjuvant chemotherapy. However he had continuous headache, abnormal eye movement at 44 months after initial treatment. Cranial MRI showed regrowing cyst. In second salvage surgery, mature teratoma was demonstrated on histopathological specimen, and we diagnosed as iGTS. Although most reported iGTSs show rapid increasing after initial chemotherapy, few reported cases show regrowth at chronic phase as our case. In long-term follow-up of germ cell tumor, iGTS is important as differential diagnosis.