IDH1 and oligodendroglioma: Main adult-type diffuse glioma entities include Astrocytoma—IDH (isocitrate dehydrogenase)-mutant (WHO grades 2–4), Oligodendroglioma—IDH-mutant and 1p/19q-codeleted (grades 2–3), and Glioblastoma—IDH wildtype (grade 4) [1,2].