Common types of primary bone cancer include osteosarcoma, a bone tumor which occurs most often in the knee and upper arm; chondrosarcoma, which begins in cartilage and occurs most often in the pelvis, upper leg, and shoulder; and the Ewing sarcoma family of tumors (ESFTs), which usually form along the backbone and pelvis, legs and arms ??? but may also arise in soft tissue such as muscle, fat, fib