IDH1 and oligodendroglioma: The tumors presented IDH1 (R132H) mutations detected by IHC and Sanger sequencing (performed for the primary tumor only) [10] and showed nuclear immunopositivity of ATRX in consistence with the 2021 WHO classification criteria for the diagnosis of oligodendroglioma, IDH-mutant and 1p/19q-codeleted.