GCT-70. INTRACRANIAL GROWING TERATOMA SYNDROME IN CHILDREN

Germ cell tumors account for less than 5% of all intracranial malignancies in children. Intracranial growing teratoma syndrome (GTS) is a rare pathophysiologic process characterized by growth of mature teratoma elements of a non-germinomatous germ cell tumor (NGGCT) during or following treatment with chemotherapy, in addition to normalization of or declining AFP/βHCG of the cerebral spinal fluid (CSF)/serum. A 13-year-old male presented with headache, emesis, and diplopia. MRI of the brain/spine revealed a localized 3.1 x 3.1 x 3.2 cm pineal tumor. Biopsy confirmed NGGCT (germinoma, immature and mature teratoma). Serum AFP (227ng/ul) and βHCG (12 IU/L) and CSF AFP (21ng/ul) and βHCG (31 IU/L) were elevated. Prior to cycle two of chemotherapy, he developed unstable gait and moderate hearing loss. Repeat MRI brain demonstrated tumor enlargement (4.4 x 5.2 x 5.1 cm) and obstructive hydrocephalus, although serum AFP/βHCG had normalized. Gross total resection of tumor confirmed GTS, without residual immature/malignant elements. Following six cycles of multiagent chemotherapy (carboplatin, etoposide, ifosfamide) and proton beam craniospinal irradiation (36 Gy with 18 Gy boost), he remains free of disease at eleven months since diagnosis. The pathogenesis of GTS remains unclear. Care must be taken to avoid misdiagnosing GTS as progressive NGGCT, as treatment and prognosis differ significantly. Second-look surgery, with a goal of complete resection, should be considered in cases of NGGCT when residual tumor grows during or following therapy, as this may represent GTS. Although histologically benign, GTS can be fatal. In patients with GTS, complete resection is usually curative.