IDH1 and central nervous system cancer: According to cIMPACT-NOW [the consortium that makes recommendations on molecular and practical approaches to central nervous system (CNS) tumor classifications] (4) and the fifth edition of the World Health Organization (WHO) Classification of Tumors of the Central Nervous System (WHO CNS5) (2021) (5), glioblastoma is no longer divided into isocitrate dehydrogenase (IDH)-wild-type and IDH-mutant groups; all glioblastomas are now classified as wild-type IDH.