The gliomas are classified into the following three types according to the fifth edition of the World Health Organization (WHO) classification of tumors of the Central Nervous System (CNS) (WHO CNS5): IDH-mutant and 1p/19q-codeleted (mut+codel) oligodendroglioma, IDH-mutant (mut+non-codel) astrocytoma, and IDH-wildtype (IDH-wild) glioblastoma (42). The gene discussed is IDH1; the disease is oligodendroglioma.