The vast majority of IDH-mutant astrocytomas are classified as G-CIMP-high, and have a superior prognosis to the G-CIMP-low subgroup, which accounts for only 6–17% of primary and recurrent tumors, and is characterized by more frequent CNA and chromothripsis, a more stem-cell-like molecular signature, and epigenetic features similar to IDH-wild-type glioblastoma [38, 56, 63, 150, 175]. This evidence concerns the gene IDH1 and glioblastoma.