In 2016, the World Health Organization (WHO) classified GBM according to the isocitrate dehydrogenase (IDH) mutation status, IDH-mutant (IDH-mt) or IDH-wild-type (IDH-wt) GBM; however, this classification has been reconsidered, as the IDH-mutant GBM aligns more closely with aggressive anaplastic astrocytomas; therefore, the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT-NOW) has since proposed that the previously defined IDH-mt GBM now be referred to as astrocytoma, IDH-mt, grade 4 [4]. The gene discussed is IDH3A; the disease is glioblastoma.