IDH1 and central nervous system cancer: The subsequent incorporation of DNA methylation profiling, based on the discovery of a CpG island methylation phenotype (CIMP) in a subset of gliomas [2], led to a refinement in the subclassification of IDH-mutant 1p/19q non-codel gliomas in G-CIMP-high and G-CIMP-low subgroups (reviewed in [3,4]).