BIOM-02. A HIGH-GRADE GLIOMA, NOT ELSEWHERE CLASSIFIED IN AN OLDER ADULT WITH DISCORDANT GENETIC AND EPIGENETIC ANALYSES

Abstract World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) uses integrated diagnoses, which incorporates both histologic and molecular features of the neoplasms. With each new iteration, there is refinement and expansion of the diagnostic categories. DNA methylation profiling is a powerful technique to diagnose existing CNS tumors and define new tumor types. However, challenging diagnostic cases that do not conform to the updated WHO classification remain. We present a case of a 72-year-old male with a high grade glioma (HGG) suggestive of high grade astrocytoma with piloid features (HGAP), but it did not “match” to HGAP on DNA methylation profiling, which is essential diagnostic criterion for HGAP. This resulted in an HGG, not elsewhere classified (NEC) diagnosis. This lack of classification posed additional challenges for treatment decision-making.