True bone cancers are sarcomas. Sarcomas can develop anywhere in the body in both soft tissue and bones. Osteosarcomas originate in the bone cells and are the most common bone cancers; they occur mostly in people who are 10 to 30 years old. Chondrosarcomas are the cancer of cartilage cells. They are rare in people under age 20 and are the second most common form of bone cancer.
Most cancers that affect bones are actually metastatic cancers that have spread to the skeletal system instead of originating there. These cancers will need to be treated based on their starting point and will not be treated as bone cancer. These include leukemia, multiple myeloma, and lymphoma.