IDH1 and oligodendroglioma: In the 2021 World Health Organization (WHO) classification of central nervous system tumors, adult-type diffuse gliomas are broadly categorized into astrocytomas, Isocitrate Dehydrogenase (IDH)-mutant, oligodendrogliomas, IDH-mutant and 1p/19q-codeleted, and glioblastomas, IDH-wildtype [1].