A hard tissue sarcoma usually involving the upper shaft of the long bones is called the osteosarcoma. This is a type of cancer that starts in the bones, the cancer cells in these type of tumor appear like early forms of bone cells that help make a new bone tissue.The first sign are the pain and swelling, pain in the affected bone is most common symptom of osteosarcoma, which often increases with activity and might result in a limp if the tumor is in a leg bone.