IDH1 and oligodendroglioma: According to the 2016 WHO classification of the brain tumors, based on morphology and molecular alterations, 44 oligodendroglioma, IDH-mutant, and 1p/19q codeleted, 93 diffuse astrocytoma, IDH-mutant, and 18 diffuse astrocytoma, IDH-wild type, were identified.