The 2021 WHO CNS classification categorizes adult diffuse gliomas into three main groups: (1) oligodendrogliomas (approximately 7% of cases, characterized by IDH mutations and 1p/19q co-deletion; (2) IDH-mutant astrocytoma (around 11%), defined by IDH mutations without 1p/19q co-deletion; and (3) IDH-wildtype glioblastomas (approximately 82%) [24]. The gene discussed is IDH2; the disease is oligodendroglioma.