IDH mutations, occurring early in glioma oncogenesis, lead to the accumulation of the oncometabolite D-2-hydroxyglutarate (2-HG), which is linked to metabolic and epigenetic dysregulation and includes inhibition of normal cellular differentiation and hypermethylation that leads to disease [21–23] (Fig. 1). This evidence concerns the gene IDH2 and central nervous system cancer.