IDH1 and glioma: In particular, aided by the inclusion of pediatric gliomas enriched in H3 mutations, the methylation data yielded four additional GBM subclassifications: those with IDH mutations (also previously described as G-CIMP tumors), PDGFRA amplifications, and those with alterations in the H3F3A/HIST1H3B/C genes (either K27 or G34 mutations).