GNAS and infection: The 2 additional on-treatment samples were from: a palliative surgical resection of a treatment-responding fibrosarcoma (other cohort) in the setting of a joint infection, which shared 62% of mutations with the baseline sample, including 2 putative drivers in GNAS and NF2; and a progressing chondrosarcoma that shared 36% of mutations from baseline, including a putative oncogenic IDH2 mutation and a distinct oncogenic TP53 alteration (missense mutation at p.G334V rather than a splicing mutation at p.T125), suggestive of convergent evolution (Supplementary Fig. 4D).