IDH1 and oligodendroglioma: The WHO classification of CNS tumors from 2016 recognizes the following types: diffuse astrocytoma, IDH-mutant (WHO grade II), anaplastic astrocytoma, IDH-mutant (WHO grade III) and glioblastoma, IDH-mutant (WHO grade IV), oligodendroglioma, IDH-mutant and 1p/19q-codeleted (WHO grade II) and anaplastic oligodendroglioma, IDH-mutant and 1p/19q-codeleted (WHO grade III) [35].