The patterns of distant metastasis and prognostic factors in patients with primary metastatic Ewing sarcoma of the bone

•The incidence of ES of the bone is very low, reaching a peak in adolescence.•We assessed the patterns of DM and the prognostic factors in this patient subset.•Lung and bone are the  most frequently distant metastatic sites.•Bone metastasis is an independent risk factor for inferior survival.