GCT-67. CENTRAL NERVOUS SYSTEM GERMINOMA IN TWO CAUCASIAN AMERICAN SIBLINGS WITH AUTISM SPECTRUM DISORDER

BACKGROUND: Central nervous system germ cell tumors (CNS-GCT) account for approximately 5% of all pediatric brain tumors. These tumors are pathologically heterogeneous, but have recurrent somatic mutations in KIT and rare germline variants in a Japanese cohort. Chromosomal abnormalities, specifically Klinefelter Syndrome, are associated with increased tumor development and familial cases have been reported, but no germline tumor syndromes are known. We describe a pair of siblings, both with autism spectrum disorder (ASD) that developed CNS-GCT, which previously has not been described outside of Japan. CASES: We report two siblings with ASD who developed CNS germinomas within two months of each other. The older brother, with basal ganglia and hypothalamic tumors, underwent surgical resection followed by treatment per ACNS0232 with chemotherapy and whole-ventricular irradiation (WVI). The younger sibling, with a midbrain tumor, also received ACNS0232, but due to poor response required additional chemotherapy and WVI. Both siblings are without evidence of disease 7 years after end of therapy. Genetic testing, including chromosomal microarray, karyotyping, and whole genome sequencing did not elucidate any variant identified as causative at that time. CONCLUSIONS: CNS-GCT are rare tumors, diverse in both histopathologic diagnosis and clinical outcomes. Currently there are known somatic alterations and germline chromosomal disorders associated with increased tumor development, but no known inheritable causes. Despite this, familial CNS-GCT have been reported in patients of Japanese descent. The description of two Caucasian American siblings with ASD and CNS-GCT is novel, refuting that familial CNS-GCT are limited to the Japanese population.