IDH1 and oligodendroglioma: With respect to the WHO tumor classification, 48.2% were glioblastoma (IDH-WT and IDH-M), 21.8% were grade II/III oligodendroglioma with 1p/19q-codeletion, 23.9% were grade II/III astrocytoma with IDH-mutation, and only 6.1% were grade II/III astrocytoma IDH-WT.