Several different kinds of tumors can grow in bones: primary bone tumors, which form from bone tissue and can be malignant (cancerous) or benign (not cancerous), and metastatic tumors (tumors that develop from cancer cells that formed elsewhere in the body and then spread to the bone). Malignant primary bone tumors (primary bone cancers) are less common than benign primary bone tumors. Both types of primary bone tumors may grow and compress healthy bone tissue, but benign tumors usually do not spread or destroy bone tissue and are rarely a threat to life.
Primary bone cancers are included in the broader category of cancers called sarcomas. (Soft-tissue sarcomas—sarcomas that begin in muscle, fat, fibrous tissue, blood vessels, or other supporting tissue of the body, including synovial sarcoma—are not addressed in this fact sheet.)
Primary bone cancer is rare. It accounts for much less than 1% of all new cancers diagnosed. In 2018, an estimated 3,450 new cases of primary bone cancer will be diagnosed in the United States (1).
Cancer that metastasizes (spreads) to the bones from other parts of the body is called metastatic (or secondary) bone cancer and is referred to by the organ or tissue in which it began—for example, as breast cancer that has metastasized to the bone. In adults, cancerous tumors that have metastasized to the bone are much more common than primary bone cancer. For example, at the end of 2008, an estimated 280,000 adults ages 18–64 years in the United States were living with metastatic cancer in bones (2).
Although most types of cancer can spread to the bone, bone metastasis is particularly likely with certain cancers, including breast and prostate cancers. Metastatic tumors in the bone can cause fractures, pain, and abnormally high levels of calcium in the blood, a condition called hypercalcemia.