Primary bone cancer, which means cancer that begins in bone tissue, is rare. According to the American Cancer Society, approximately 2,380 new cases of primary bone cancer will be diagnosed in 2008 — a figure that represents less than 0.2 percent of all cancers.
Primary bone cancer can grow in any of the 206 bones of the adult human body, but it occurs most often in the long bones of the arms and legs. Although bone cancer can present itself at any age, the most common types occur in children and young adults. Bone cancers form in the cells that make hard bone tissue. Cancers that arise in the cells produced in the bone marrow, such as leukemia, multiple myeloma, and lymphoma, are not considered bone cancers, although they do affect the bone and may require orthopaedic management.
Benign (noncancerous) bone tumors are more common than malignant (cancerous) ones. Although benign tumors do not spread and are rarely life threatening, both types may grow and compress healthy bone tissue and absorb or replace it with abnormal tissue.
Osteosarcoma is the most common type of primary bone cancer, making up 35 percent of bone cancer cases. This cancer affects primarily children and young adults between the ages of ten and 25. Osteosarcoma often starts in the ends of bones, where new tissue forms as children grow. It occurs most often in the knee.
Chondrosarcomas, one of the most common types of bone cancer in adults over age 50, form in cartilage — usually around the pelvis, knee, shoulder, or upper part of the thigh. These cancers make up 26 percent of all bone cancer cases.
Ewing’s sarcoma usually occurs in the middle part of bones, arising most often in the hip, ribs, upper arm, and thighbone. Like osteosarcoma, this cancer affects primarily children and young adults between the ages of ten and 25. Ewing’s sarcoma is responsible for 16 percent of bone cancer cases.
The following types of bone cancer are rare and occur primarily in adults:
- Fibrosarcomas usually appear in the knee or hip area. They can arise in older patients after radiation therapy for other cancers.
- Giant cell tumors, which usually begin in the knee, affect young adults most frequently, and women more often than men.
- Adamantinomas usually occur in the shinbone.
- Chordomas are found most often in the sacrum, which is the lower part of the spine, also known as the tailbone.
Metastatic Cancer to Bone
Metastatic bone cancer — cancer that starts somewhere else in the body and then spreads to the bone — is much more common than primary bone cancer. Although any type of cancer can spread to the bone, the most common types are those of the breast, lung, kidney, thyroid, and prostate. Bone metastases most often arise in the hip, femur (thighbone), shoulder, and spine. Like other types of cancer, those that start in the bone can also spread to other parts of the body.
Among those who develop bone cancer, 95 percent of people do not have any obvious risk factors. While scientists are not certain what causes bone cancer, a number of factors that may increase a person’s risk have been identified:
Bone cancers occur more frequently in children and young adults, particularly those who have had radiation therapy or chemotherapy for other conditions. Bone cancers that appear in young people may also be associated with the rapid growth of bones that occurs during puberty.
A small number of bone cancers are due to heredity. For example, children with hereditary retinoblastoma (an uncommon cancer of the eye) are at a higher risk of developing osteosarcoma. Another hereditary condition that may increase bone cancer risk is Li-Fraumeni syndrome, a disorder caused by a mutation in the p53 tumor suppressor gene. This syndrome predisposes people to cancers of the breast and brain, osteosarcoma, and other types of sarcoma.
Adults with Paget’s disease, a noncancerous condition characterized by abnormal development of new bone cells, may be at increased risk for osteosarcoma. Bones affected by Paget’s disease are heavier and thicker, yet weaker than normal bones, and more likely to fracture.
The most common symptom of bone cancer is pain, which is caused either by the spread of the tumor or by the breaking of bone that is weakened by a tumor. Stiffness or tenderness in the bone may also occur. Sometimes there are other symptoms, such as fatigue, fever, swelling, and stumbling. But these symptoms can also be caused by other conditions. Only a doctor can tell for sure whether or not a patient has bone cancer.