Notably, a portion of IDH-mutant astrocytomas, including tumors which were designated WHO grade 4 at initial presentation, were relatively stable; ~ 35% maintained a G-CIMP-high status and ~ 15% moved to an intermediate epigenetic phenotype, suggesting that this progression is related to but not completely dependent upon grade [55]. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).