TBIO-13. USE OF NEXT GENERATION SEQUENCING TO IDENTIFY MOVE DRIVERS OF CRYPTIC, CLINICALLY AGGRESSIVE BRAIN TUMORS

INTRODUCTION: Next generation sequencing (NGS) is an emerging technology which allows for in-depth analysis of pediatric brain tumors. NGS has particular use in the context of ambiguous or aggressive neoplasms, where it can be leveraged to discover novel drivers, inform pathologic classification, and direct targeted therapies. OBJECTIVE: The objective of this case series was to utilize NGS technology to illuminate the biology of aggressive brain tumors with ambiguous pathologic features and clinically aggressive behavior. METHODS: FFPE tumor tissue and matched germline DNA were subjected to whole exome sequencing (WES). Data were analyzed according to the GATK pipeline. RESULTS: The first case is a 6-year-old male who presented with innumerable foci of leptomeningeal nodules throughout the neuroaxis. Original pathology was CNS embryonal tumor. WES identified loss of chromosome 1p and 16q with gain of 1q and amplification of MYC and OTX2 loci (cytogenetic aberrations characteristic of group 3 medulloblastoma) and a deleterious mutation in BCL7B, a known tumor suppressor gene. The second case is a 2-year-old female who presented with a parietal lobe mass diagnosed as high grade neuroepithelial tumor with C11orf95 translocation, but no RELA fusion. WES revealed loss of small region of chromosome 2p and mutations in IDH3G, TRAF2, and JMJD1C, suggesting novel targets for further study. CONCLUSIONS: In both cases, NGS studies were able to shed light on the underlying tumor biology and/or refine the pathologic diagnosis. These data underscore the utility of applying NGS technology to study the biology of pediatric brain tumors.