IDH1/2 mutations occur frequently in low-grade glioma and secondary glioblastoma (~80%), but can also occur in acute myeloid leukemia (20%), angioimmunoblastic T-cell lymphomas (20%), and rarely in other malignancies such as thyroid, colorectal, and prostate cancer (Table 1) (Kang et al., 2009; Yen et al., 2010; Ghiam et al., 2012; Ohgaki and Kleihues, 2013; Yen et al., 2017). The gene discussed is IDH1; the disease is central nervous system cancer.