EP12.11 SYNCHRONOUS WHO GRADE 3 OLIGODENDROGLIOMA AND GRADE 4 ASTROCYTOMA: A CASE REPORT

Abstract Since the introduction of the fifth edition of the WHO Classification of Tumors of the Central Nervous System, glioma diagnosis has become more standardized and heavily reliant on molecular characteristics. Consequently, the co-occurrence of distinct glioma subtypes within a single patient is exceedingly rare. We report the case of a 59-year-old patient who presented with seizures and was found to have two spatially distinct brain tumors: one in the right fronto-temporo-insular region and the other in the left frontal lobe. The maximum diameters of the right and left tumors were 8.9 cm and 4.6 cm, respectively. MRI of the left frontal lesion revealed heterogeneous contrast enhancement. Gross total resection of the left frontal tumor was performed first; the tumor involved the dorsolateral prefrontal cortex, including the supplementary motor area, and contained xanthochromic fluid. Histopathological and molecular analysis yielded an integrated diagnosis of oligodendroglioma, IDH-mutant and 1p/19q-codeleted, CNS WHO grade 3. Subsequently, near-total resection of the right tumor was performed. This tumor involved the frontal pole, entorhinal cortex, frontal horn, caudate nucleus, corpus callosum, insula, internal capsule, and temporal pole, with necrosis observed near the internal capsule. Molecular profiling revealed absence of 1p/19q codeletion, leading to a diagnosis of astrocytoma, IDH-mutant, CNS WHO grade 4. Following both surgeries, the patient remained seizure-free and maintained a good performance status. Adjuvant radiotherapy (60 Gy in 30 fractions) and six cycles of PCV chemotherapy were administered. Although the pathogenesis of multicentric gliomas remains unclear, this case supports the hypothesis of a single-cell progenitor origin in gliomagenesis.