The last 5th edition of the World Health Organization (WHO) classification of CNS tumors released in 2021 proposes a refinement of the classification of adult-type diffuse gliomas based on molecular profiles, largely dependent on isocitrate dehydrogenase 1 or 2 (IDH1/2) mutation status and 1p/19q codeletion status, resulting in 3 primary tumor subtypes: IDH-mutant, 1p/19q codeleted oligodendroglioma; IDH-mutant astrocytoma; and IDH-wildtype glioblastoma [2]. This evidence concerns the gene IDH1 and oligodendroglioma.