Ewing sarcoma is cancer that occurs primarily in the bone or soft tissue. While Ewing sarcoma can develop in any bone, it is most often found in the hip bones, ribs, or long bones (e.g., femur (thighbone), tibia (shinbone) or humerus (upper arm bone)).
https://www.hopkinsmedicine.org/health/conditions-and-diseases/sarcoma/ewing-sarcoma-in-adults