Bone Cancer, malignant tumor that involves the skeletal system. Some cases of bone cancer are caused by malignant tumors that arise directly within the bones or joints. Such tumors are called primary malignant tumors. In contrast, metastatic malignant tumors originate elsewhere in the body and then later invade the bones or joints, usually by way of the bloodstream or the lymphatic system.
Primary malignant tumors, or sarcomas, include osteosarcomas from bone cells, chondrosarcomas from cartilage cells, malignant fibrohistiocytomas and fibrosarcomas from fibrous supportive elements, and lymphomas and Ewing's sarcoma from the bone marrow. Although all bones are susceptible to cancer, the region surrounding the knee accounts for most tumors. The most common primary bone malignancies are osteosarcomas, which are slightly more common among males than females.
Symptoms of Bone Cancer
The classic symptom for osteosarcoma is a slowly growing mass. Although not painful to the touch, the tumor itself is usually characterized by a dull discomfort that persists at night. Because the tumor develops so slowly, the cancer often progresses quite far before being diagnosed.
Diagnosis can be made using several means. X-ray examination reveals a structural change near the end of the bone and, frequently, abnormal bone formation within the tumor mass. Radionuclide bone scan, a process that assesses uptake of injected radioactive material by bone, would be positive, indicating active bone formation. In addition, computerized axial tomography (CT or CAT) scan would demonstrate enlargement of the outer portion, or cortex, of the bone, along with a soft tissue mass outside the bone. Lastly, arteriography, an X-ray procedure involving the use of dyes to identify affected arteries, would help to define the extent of the tumor. Since osteosarcomas ultimately spread by way of the bloodstream to the lungs, chest X rays are necessary to determine evidence of metastasis.
The critical diagnostic test is a biopsy, in which tissue is removed for examination. If bone cancer is present, a microscopic examination of the removed tissue will show abnormal cells producing unmineralized bone.
The treatment program for bone cancer is usually based on the knowledge that over 80 percent of the patients will have secondary tumors, or metastases, elsewhere in the body at the time of diagnosis. In addition, metastases affecting bone cause pain and may lead to a structural weakness of the bone that results in fractures. Tumor control throughout the body is therefore as essential as local control. Metastatic bone disease often responds to therapeutic radiology. Most cancer centers also use chemotherapy to destroy small blood-borne metastases when local surgery is performed. Local tumors can be eradicated by amputating the limb above the tumor or by removing the tumor area while preserving the limb intact. Preservation of the limb is only possible if the tumor is detected before it has invaded the surrounding nerves and blood vessels. See also Cancer.