IDH1 and glioblastoma: Presented the findings of the working group for grading criteria and terminologies in IDH-mutant astrocytomas in the fifth update for cIMPACT-NOW. Suggested that if CDKN2A/B homozygous deletion, necrosis, or microvascular proliferation were present, a grade 4 designation was appropriate. The term IDH-mutant glioblastoma would no longer exist.