It first divided the diffuse glioma into adult and child types, with the adult type divided into three types: astrocytoma, isocitrate dehydrogenase (IDH)‐mutant; oligodendroglioma, IDH‐mutant and 1p/19q co‐deleted; and glioblastoma, IDH wild type. The gene discussed is IDH1; the disease is oligodendroglioma.