IDH1 and oligodendroglioma: The 2016 World Health Organization (WHO) classification of tumors of the central nervous system (CNS) classified diffuse gliomas by both histological and molecular features such as IDH1 (isocitrate dehydrogenase 1)-mutant and wild-type glioblastoma, IDH1-mutant and chromosome 1p/19q codeleted oligodendrogliomas, and other gliomas [2].