The latest 2021 WHO classification of central nervous system tumors relies even further on these biomarkers to classify diffuse gliomas into three main types: IDH-wildtype GBM, IDH-mutant astrocytoma, and IDH-mutant and 1p/19q codeleted oligodendroglioma [19]. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).