IDH1 and oligodendroglioma: Based on the revised WHO classification, tumor samples from their first surgery were diagnosed as 22 diffuse astrocytomas, IDH-mutant, 9 anaplastic astrocytomas, IDH-mutant, 17 oligodendrogliomas, IDH-mutant and 1p/19q co-deleted, 12 anaplastic oligodendrogliomas, IDH-mutant and 1p/19q co-deleted, and 5 oligodendrogliomas, NOS, indicating that all IDH mutant gliomas enrolled in this study were categorized as lower grade gliomas.