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Causes and Incidence Few known risk factors exist. Individuals with prior radiation, Paget's disease, fibrous dysplasia, or enchondromatosis are at greater risk. Primary bone tumors are rare, accounting for only 0.2% of all malignancies in the United States. The tumors affect primarily adolescents and adults over 65 years of age.

Disease Process Osteosarcomas are the most common primary bone tumor. Cancer cells originate in the mesenchyma of the medullary cavity of the bone (usually long bones around or in the knee) and proliferate rapidly, absorbing normal bone and promoting tissue destruction. The bone becomes sclerotic or lytic, or both, and an aggressive periosteal reaction ensues, accompanied by a soft tissue mass. The lungs are the most common metastatic site; spread to regional lymph nodes is rare. Fibrous tumors are similar in character to osteosarcomas.

Symptoms An initially painless mass is the most common presenting sign. Pain or swelling (or both) at the affected site is also common.

Potential Complications Pathologic fractures occur with progressive destruction of normal bone tissue.

Diagnostic Tests X-rays and bone scans of the involved bone allow visualization of the tumor. The definitive diagnosis is made through biopsy of the tumor.

Treatments

Surgery

En bloc resection and reconstruction of affected limb; amputation of affected limb

Drugs

Systemic chemotherapy with methotrexate; intraarterial perfusion with doxorubicin as an adjunct before surgery

General

Radiation used with Ewing's sarcoma; rehabilitation after amputation; gait training; fitting of prosthesis