Many noncancerous (benign) bone abnormalities may resemble bone tumors but are not.
Unicameral Bone Cyst:
Unicameral bone cysts occur near the parts of the bone from which growth occurs (growth plates) in the arms or legs in children. The cysts often cause nearby bones to thin, which can lead to a fracture. Cysts may heal and may disappear as the fracture heals. Most often, these cysts are treated by injection with corticosteroids, often repeatedly, processed bone putty, or synthetic bone substitutes. Cysts that are more than 2 inches (about 5 centimeters) long or wide, particularly in children, may require surgery to remove the contents of the cyst from the bone by scraping it with a scoop-shaped instrument (curettage) and transplantation of bone from one site to another (bone grafting). However, many people with these cysts respond to injections rather than invasive surgery. Regardless of treatment, the cyst remains or recurs in about 10 to 15% of people.
Fibrous dysplasia involves abnormal bone development during childhood. It may affect one bone or several bones. Birth marks and signs of early puberty (see see Sidebar: Early Puberty) may be present; this is also called Albright's syndrome. The abnormal bone growths commonly stop developing at puberty. This condition rarely becomes cancerous (malignant). Calcitonin injections or bisphosphonates administered intravenously may help relieve the pain. A surgical procedure may correct deformities, fractures that do not heal with casting, or pain that cannot be relieved any other way.
Aneurysmal Bone Cyst:
Aneurysmal bone cysts usually develop before people reach age 25, and the cause is not known. These cysts usually occur near the outer ends of the long bones (upper arm and thigh bones), but almost any bone may be affected. The cyst tends to grow slowly. A new bone shell forms around the cyst and is often wider than the original bone. Pain and swelling are common. The cyst may be present for a few weeks to a year before diagnosis.
Surgical removal of the entire cyst is the most successful treatment, but sometimes the cysts recur if they are not removed completely. Radiation should be avoided when possible because cancerous tumors occasionally develop later. However, radiation may be the treatment of choice for cysts that cannot be treated surgically and are compressing the spinal cord.
Last full review/revision April 2008 by Michael J. Joyce, MD