IDH1 and central nervous system cancer: The isocitrate dehydrogenase gene 1 and 2 (IDH1/IDH2) mutational status and the hypermethylator phenotype [glioma CpG island methylator phenotype (G‐CIMP)], both characteristic of secondary GBMs and associated with longer survival times, were then considered to improve the TCGA classification (Noushmehr et al., 2010; Turkalp et al., 2014).