The two most important molecular biomarkers, wildtype or mutant isocitrate dehydrogenase 1/2 (IDH) and the 1p19q codeletion, differentiate adult-type diffuse gliomas into oligodendroglioma (IDH mutant and 1p19q codeleted), astrocytoma (IDH mutant), and GBM (IDH wildtype) [2]. The gene discussed is IDH2; the disease is astrocytoma (excluding glioblastoma).