There has been additional characterization of hemizygous CDKN2A/B loss in meningioma, with multiple studies demonstrating even one copy loss rapidly accelerates the time to meningioma recurrence.23–25 Collectively, these data support the expansion of molecular grading criteria for aggressive IDH1/2-mutant astrocytomas to include both hemizygous and homozygous CDKN2A/B loss. The gene discussed is IDH1; the disease is meningioma.