IDH1 and oligodendroglioma: According to the fifth edition of WHO Central Nervous System Tumor Classification (CNS5 WHO), adult-type diffuse gliomas are divided into three categories: glioblastoma, IDH wild type (grade 4); Oligodendroglioma, IDH mutant, 1p/19q co-deletion, (grade 2 and 3); Astrocytoma, IDH mutant (grade 2, 3 and 4) [2].