In high‐grade gliomas, IDH mutations stratify GBM into (a) primary GBMs (pGBM), IDH wild‐type tumors, which do not show clinical or histopathological evidence of stemming from a precursor lesion, and (b) secondary GBMs (sGBMs), which develops from lower‐grade tumors and exhibit IDH mutations (Gupta et al., 2011; Louis et al., 2016). The gene discussed is IDH2; the disease is central nervous system cancer.