Bone cancer: A malignancy of bone. Primary bone cancer (cancer that begins in bone) is rare, but it is not unusual for cancers to metastasize (spread) to bone from other parts of the body, such as the breast, lung, and prostate. The most common type of primary bone cancer is osteosarcoma, which develops in new tissue in growing bones. Another type of cancer, chondrosarcoma, arises in cartilage. Ewing's sarcoma begins in immature nerve tissue in bone marrow. Osteosarcoma and Ewing's sarcoma tend to occur in children and adolescents, and chondrosarcoma occurs most often in adults. Pain is the most frequent symptom of primary and metastatic cancer in bone. Bone cancer can also interfere with normal movements and can weaken the bones, leading to fractures. Diagnosis of bone cancer is supported by findings of the medical history and examination, blood tests (including measuring the level of the enzyme for the enzyme alkaline phosphatase), and X-ray studies, and it is confirmed by a biopsy. Treatment depends on the type, location, size, and extent of the tumor. Surgery is often the primary treatment. Although amputation of a limb is sometimes necessary for primary bone cancer, chemotherapy has made limb-sparing surgery possible in many cases. Radiation may also be used.