IDH3A and glioblastoma: The World Health Organization CNS5 classification categorizes adult glioblastoma multiform (GBM) as isocitrate dehydrogenase wild-type adult-type diffuse astrocytoma with one or more biomarkers, such as necrosis, microvascular proliferation, mutation of the TERT promoter gene, chromosomes +7/-10 copy number changes, or amplification of endothelial growth factor receptor (EGFR) genes (1).