IDH1 and glioblastoma: Based on DNA methylation in CNS tumors, Capper and co-workers grouped most of the IDH-mutant astrocytoma, WHO grade 4, into methylation subclass “A IDH, HG”, while IDH wild-type GBM were stratified into seven methylation classes (“GBM, G34“, “GBM, RTK I”, “GBM, RTK II”, “GBM, RTK III”, “GBM, MES”, “GBM, MID”, “GBM, MYCN”) [52].