IDH2 and glioblastoma: All samples grouped together as IDH-mutant astrocytoma, high-grade, by the brain tumor classifier and t-SNE plotting (Fig. 4); however, more detailed analysis revealed measurable molecular divergence and subclustering between the initial biopsy and the GBM masses found in the right and left hemispheres regarding their distinct copy number profile alterations, alterations in specific methylation sites, and loss of MGMT promoter methylation (Figs. 3, 4, 5).