The other category of sarcoma is bone cancer. It is very rare, with approximately 3,000 new cases diagnosed in the United States each year. The incidence is slightly higher in males than females. No race has a higher incidence than another, although Ewing’s sarcoma is particularly rare among African and American blacks. Due to the rarity and severity of bone cancer, a bone cancer specialist such as an orthopaedic oncologist should be consulted in the treatment of this disease. Visit the Musculoskeletal Tumor Society to find a sarcoma surgeon.
Bones consist of three types of tissue: compact tissue, the hard outer portion of the bone; cancellous tissue, the spongy tissue inside the bone containing the bone marrow; and subchondral tissue, the smooth bone tissue of the joints. Cartilage surrounds the subchondral tissue to form a cushion around the joints.
Bone tumors can be benign (non-cancerous) or malignant (cancerous). Benign bone tumors are rarely life threatening, and do not spread within the body; however, they can grow and compress healthy bone tissue. Cancer that develops in the bone is called primary bone cancer. It is differentiated from secondary bone cancer, which spreads to the bone from another part of the body.
Scientists are uncertain about what causes bone cancer, but they have been able to identify certain factors that may put a person at risk. Children and young adults who have undergone radiation therapy or chemotherapy for other diseases are at an increased risk for bone cancer. Additionally, adults with Paget's disease, which is a disease characterized by abnormal growth of new bone cells, have an increased risk of osteosarcoma. There are also some hereditary conditions that can increase the risk of bone cancer.
Symptoms of bone cancer can vary depending on the size and location of the tumor. Pain is the most common symptom. Tumors arising in or around the joints often cause swelling and tenderness. Tumors also can weaken the bones, causing fractures. Other symptoms can include weight loss, fatigue, and anemia.
The first step in diagnosing primary bone cancer is a complete medical history and a physical examination performed by a physician. The doctor may order a blood test to determine the level of an enzyme called alkaline phosphatase. Approximately 55% of patients with primary bone cancer will have elevated levels of alkaline phosphatase. However, it isn't a completely reliable indicator for bone cancer, because growing bones in children will also cause the enzyme to be elevated.
X-rays are also used to locate a bone tumor. If an x-ray suggests that a bone tumor is present, a doctor may order further testing, such as a CT scan, Magnetic Resonance Imaging (MRI), or a bone scan. Finally, a biopsy must be performed to determine if cancer is present.
A biopsy is a procedure used to remove sample tissue from the tumor. A surgeon, usually an orthopaedic oncologist, performs either a needle biopsy or an incisional biopsy. During a needle biopsy, the surgeon makes a small hole in the bone and removes sample tissue with a small instrument. For an incisional biopsy, the surgeon cuts into the tumor and removes sample tissue. Certain tumors are can be appropriately biopsied by a radiologist using imaging guidance with a CT scan or under ultrasound. A pathologist—a doctor specializing in identifying disease—will then study the cells and tissues under a microscope to determine whether the tumor is cancerous.
The treatment of bone cancer depends on the size, location, type, and stage of the cancer. Surgery is often the primary treatment. While amputation of a limb is sometimes necessary, using chemotherapy either before or after surgery has allowed physicians to save the limb in many cases. Radiation is also used sometimes, in combination with the other treatments.
New and more effective treatments are being developed in clinical trials at many sarcoma centers and cancer centers. The most common types of bone sarcomas are described below.
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