IDH2 and oligodendroglioma: Based on the mutational status of IDH1/2 and the presence of chromosome 1p and 19q deletion, adult-type diffuse gliomas are classified as astrocytoma IDH-mutant (grades 2, 3, or 4), oligodendroglioma IDH-mutant and 1p/19q codeleted (grades 2 or 3), and glioblastoma (GBM) IDH-wildtype (grade 4) [2].