Adult-type diffuse gliomas have been consolidated to three tumor types, which can be further graded histologically (mitotic count, necrosis microvascular proliferation) or by the presence of certain molecular alterations.Oligodendroglioma, IDH-mutant and 1p/19q-codeletedis defined by the presence of eitherIDH1orIDH2hotspot mutations as well as whole chromosome arm deletions of 1p and 19q (22). Here, IDH1 is linked to oligodendroglioma.