IDH1 and oligodendroglioma: Adult-type diffuse gliomas are prevalent CNS tumors and include three genotype-based, peculiar types of tumors: (1) astrocytoma, IDH-mutant, (2) oligodendroglioma, IDH-mutant and 1p/19q-co-deleted, and (3) glioblastoma (GBM), IDH-wildtype [7].