Based on histological and radiological features, HGGs are subclassified into the following groups: anaplastic astrocytoma (grade III), IDH wild-type glioblastoma (grade IV), IDH-mutant glioblastoma (grade IV), H3K27M-mutant diffuse midline glioma (grade IV), IDH-mutant with 1p/19q co-deletion anaplastic oligodendroglioma (grade III), and pleomorphic anaplastic xanthoastrocytoma (grade III). The gene discussed is IDH1; the disease is anaplastic oligodendroglioma.