According to the fifth edition of the WHO Classification of Tumors of the Central Nervous System, published in 2021, adult-type diffuse gliomas are classified into three subtypes: astrocytoma (IDH-mutant), oligodendroglioma (IDH-mutant and 1p/19-codeleted), and glioblastoma (IDH-wildtype) [33]. Here, IDH1 is linked to oligodendroglioma.