INNV-02. Central nervous system tumor with BCOR/BCORL1 fusion: a rare and novel CNS tumor entity treated with radiation and temozolomide

Abstract The Central Nervous System (CNS) tumor with BCL6 Corepressor (BCOR) tumors are newly identified tumor entities as of the 2021 World (WHO) Classification of CNS Tumors. With less than 50 cases reported in literature to date, these tumors can mimic ependymomas and are diagnosed with a distinct DNA-methylation profile. No standard of care therapy exists due to the rarity of this tumor, with only cases reported in literature to date. Predominantly occurring in children, adult cases are exceptional and the optimal treatment is unknown. We present a case of a 37 year old female with a midline CNS Tumor with BCOR/BCORL1 fusion diagnosed with DNA methylation profiling. On histopathologic examination, a densely cellular and mitotically active neoplasm with innumerable pseudorosettes was observed. GFAP and Olig2 were positive. Though no BCOR/BCORL1 fusions were noted, a pathogenic BCOR p.S209Cfs*7 variant coupled with 2 EGFR variants (p.G598V and p.T363I) were uncovered. She was successfully treated with chemoradiation. Our case adds to the small, but growing body of evidence supporting the use of radiation and temozolomide for this rare and new CNS tumor entity.