With the discovery of isocitrate dehydrogenase (IDH) mutation as a key driver of gliomagenesis in 25–30% of infiltrating gliomas and its correlation with a favorable prognosis, recent consensus guidelines regard IDH-mutant (IDHmut) tumors as biologically distinct entities from IDH-wildtype (IDHwt) tumors, and indeed the term ‘glioblastoma’ is now only applied to IDHwt infiltrating astrocytomas with high-grade histological/molecular features1,10–12. The gene discussed is IDH2; the disease is central nervous system cancer.