A patient with relapsed Ewing sarcoma, zccs276, with STAG2 loss, which in a recent study that included both Ewing sarcoma mouse and larval zebrafish xenografts was associated with enhanced metastatic potential of Ewing sarcoma (34), experienced a PR of the target lesion to olaparib/TMZ with concurrent development of a new lesion before stopping treatment due to TMZ toxicity. This evidence concerns the gene STAG2 and Ewing sarcoma.