The remaining 3/45(7%) gliomas were verified as IDH1-negative by both IDH1R132H immunostaining and IDH1 sequencing; IDH2 sequencing showed no mutation in 2/3 of these cases, with the third case being unanalyzable but unlikely IDH2 mutated (p53-negative, 1p/19q intact). This evidence concerns the gene IDH2 and central nervous system cancer.