Moreover, in 2021, the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5) reclassified GBM—removing the isocitrate dehydrogenase (IDH) mutation type from GBM and adding the IDH-wild-type diffuse astrocytoma in adults with TERT promoter mutation or EGFR gene amplification or +7/−10 chromosome copy number changes (2). The gene discussed is IDH3A; the disease is glioblastoma.