Lower-grade gliomas share molecular features with secondary GBMs and with a subset of primary GBMs, including frequent IDH mutations (>70%) [10, 12, 19], a proneural gene expression signature [6, 7, 20], and a glioma CpG island hypermethylator phenotype (G-CIMP) [8]. The gene discussed is IDH2; the disease is central nervous system cancer.