IDH1 and glioma: Using clustering of IDH-mutant gliomas, Ceccarelli et al. observed existence of three major glioma groups: Codel, IDH-mutant 1p/19q codeleted low grade gliomas; glioma CpG island methylator phenotype (G-CIMP)-low, IDH-mutant non-1p/19q codeleted low and high grade gliomas with low genome-wide DNA methylation; and G-CIMP-high, IDH-mutant non-1p/19q codeleted low and high grade gliomas with higher level of genome-wide DNA methylation (92).