Sturm and colleagues identify six subgroups of GBM that vary in both clinical and mutational variables associated with individual methylation subgroups; three of which are delineated by mutations shown to affect the histone code, namely H3.3 K27M, H3.3 G34R/V and IDH1 R132-mutated tumors [66]. Here, IDH1 is linked to glioblastoma.