IDH1 and astrocytoma (excluding glioblastoma): The genetic heterogeneity of adult gliomas have been incorporated into a refined classification system, as per the 2021 WHO classification of tumors of the central nervous system, which delineates gliomas into 3 subtypes: isocitrate dehydrogenase-WT (IDH-WT) glioblastoma (GBM), astrocytoma with IDH mutation (mut), and oligodendroglioma with IDH mut and a 1p/19q codeletion (2).