IDH1 and glioblastoma: Grade 4 IDH1/2-mutant astrocytomas and glioblastomas were more genomically distant from each other (median JD: 0.147) compared to genomic differences within grade 4 IDH1/2-mutant astrocytomas (median JD: 0.088) or within glioblastomas (median JD: 0.088, P < .001, Figure 3D).