Diseases & Conditions
Nonossifying fibromas (NOFs) are the most common benign bone tumor in children. It is estimated that 30 to 40% of people under the age of 20 have an NOF, although few will have any symptoms. NOFs are often discovered by chance when a patient requires X-rays for another reason, such as a knee injury.
These tumors occur almost twice as often in males as in females. They do not become cancerous and they do not spread to other parts of the body (metastasize). In most cases, no treatment is necessary because NOFs typically go away on their own when a child is fully grown.
Nonossifying fibromas are made of fibrous tissue and are typically yellow or brown in color. They most often occur in the flared end of the lower femur (thighbone) and in the flared upper or lower ends of the tibia (shinbone). NOFs also sometimes occur in the fibula (the smaller bone in the lower leg) and in the humerus (upper arm bone).
A small percentage of people with NOF will have more than one tumor. It is uncommon, however, to have more than two or three tumors except in certain very rare conditions (such as neurofibromatosis or Jaffe-Campanacci syndrome).
Nonossifying fibromas are also known as metaphyseal fibrous defects, fibrous cortical defects, non-osteogenic fibromas, or cortical desmoids.
The cause of NOF is not known. There are also no known factors that put you at greater risk for the tumors — such as genetics, the environment, or traumatic injury.
Most children with an NOF will have no symptoms at all. Many times, the tumor is discovered incidentally when X-rays are taken for another reason.
Some patients will have mild swelling and tenderness to the touch over the NOF. A small percentage will report a constant dull ache that is not associated with activity. This pain may be due to the tumor itself or may be the result of a crack in the bone (pathologic fracture). These minor fractures can occur because an NOF weakens the overall strength of the bone. A fracture is more likely to occur when the NOF is large.
To diagnose an NOF, the doctor will take a complete medical history and conduct a physical examination. They will also order imaging tests — most important, X-rays.
X-rays. X-rays provide clear images of dense structures, such as bone. In an X-ray image, an NOF appears dark with a thin surrounding white rim.
Other imaging tests. In certain cases, a computerized tomography (CT) scan, magnetic resonance imaging (MRI) scan, or bone scan may be needed to further evaluate the tumor.
Although not always necessary, a CT scan or MRI can show the exact size of the tumor, as well as any change in its appearance over time. These images can also show cortical integrity (how thin the strong outer portion of the bone is in the region of the NOF) or a pathologic fracture.
A bone scan is sometimes helpful to see if there is more than one tumor.
Observation. In most cases, no treatment is needed for an NOF other than simple observation. If left alone, NOFs stop growing when the adolescent finishes growing. Over time, the tumor will fill in with bone. Most NOFs disappear by the time a person reaches their early 20s. Until this time, the doctor may recommend periodic X-rays.
In certain cases, surgical treatment should be considered. This include instances of large NOFs, particularly in a young child who has a lot of growth left, or when symptoms are present. Large size or the presence of symptoms can indicate that the bone is weak and likely to fracture, even with very little force.
Curettage. This is the surgical procedure most commonly used to treat NOFs. In curettage, special instruments are used to scrape the tumor out of the bone.
Bone graft. After curettage, the doctor will fill the hole with a bone graft to help stabilize the bone. A bone graft may be taken either from a donor (allograft) or from another bone in the body (autograft). The doctor may also use a bone cement mixture to fill the hole.
Most patients are able to return to full activity, including sports, by 3 to 6 months after surgery. Factors that may impact recovery time include:
- The size of the NOF
- The type of bone graft used
- How quickly the bone heals
Whether or not treatment was needed, most patients with an NOF should return to their doctor regularly for X-rays to make sure the tumor is not coming back or growing.
The long-term outlook for patients with NOF is very good. These tumors resolve with skeletal maturity, do not become cancerous, and rarely recur if treated surgically.
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