IDH2 and central nervous system cancer: Remarkably, more than 70% of grade II-III gliomas and secondary GBMs were found to bear mutations in IDH1 or IDH2. Both the IDH1 and IDH2 mutations were highly conserved, confined to a single residue, R132 and R172, respectively, and most frequently a single allele was mutated with the wild type allele retained [1].