In view of the importance of the glial genotype for patient management and prognosis, the current classification (WHO 2021) attributes a pivotal role to IDH and 1p19q status for the discrimination between tumor subtypes (astrocytoma, IDH mutant [IDHm]; oligodendroglioma, IDHm and 1p19q codeleted; and glioblastoma, IDHm or IDH wild-type [IDHwt]) [2]. This evidence concerns the gene IDH1 and oligodendroglioma.