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Non-ossifying fibromas are the most common benign bone tumor in children, affecting up to 40%. They are made of fibrous tissue and grow on long bones, especially the legs. They usually appear as a solitary growth. They don’t spread or turn to cancer. Non-ossifying fibromas go away on their own when the child has fully grown.
A non-ossifying fibroma is a benign bone tumor made up of fibrous tissue, like scar tissue. It is one of many kinds of non-cancerous growths that occur for unknown reasons. Tumors are essentially uncontrolled cell growth in a particular spot. “Fibroma” means fibrous (fibr) tumor (oma). “Non-ossifying” means that the tumor doesn’t calcify into bone tissue. The fibroma grows on bones, but it is not made of bone, as some others are.
Non-ossifying fibromas occur in as many as 20% to 40% of healthy children. They often appear at the end of the thighbone or shinbone where it meets the knee, and less commonly on other long bones. They usually occur as a single growth, though occasionally there might be two or three. They do not spread or become cancerous, and they rarely cause any symptoms at all. They grow until the skeleton is done growing and then go away on their own.
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“Ossifying” means turning into bone, or bone-like tissue. An ossifying fibroma is made up of bone tissue or includes bone parts. It grows out of connective tissue and creates bone where there wasn’t any before. A non-ossifying fibroma is non-bone tissue that grows on bones. When the non-ossifying fibroma heals, it gets filled in by the surrounding bone cells, and at this point, it is not considered a tumor anymore.
No. Although some kinds of benign bone tumors have a low chance of becoming cancerous over time, the non-ossifying fibroma is not one of them. You’ll never have to worry about that with this one.
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Non-ossifying fibromas are the most common benign bone tumors in children, affecting as many as 20-40%. They are twice as common in boys as they are in girls. They peak between the ages of 10 to 15 and generally recede by the age of 25. Many people may never know they had one.
There is no known cause, genetic link, or risk factor involved in the growth of a non-ossifying fibroma (or even two or three). Multiple non-ossifying fibromas are very rare and are associated with two specific conditions: neurofibromatosis and Jaffe-Campanacci Syndrome.
The tumor itself is not painful. If it grows big enough, it may cause some swelling and tenderness under your skin, especially during activities that may irritate it. Most non-ossifying fibromas don’t grow big enough to cause any symptoms.
Rarely, a large tumor may weaken the structure of the growing bone it's attached to, causing the bone to fracture. If your child has a dull, constant pain at the site of the tumor, it's more likely a fracture, not the tumor, that they are feeling.
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Since most non-ossifying fibromas cause no symptoms, they are often discovered by accident on X-rays taken for another reason. Sometimes they are discovered after they have weakened the bone and contributed to a fracture.
If you’ve noticed a hard lump on one of your long bones or on one of your child’s, you might want to get an X-ray to have it diagnosed, even if it’s causing no symptoms. It might be a non-ossifying fibroma or another kind of benign bone tumor.
Your healthcare provider will ask about your symptoms and health history and then order imaging tests.
X-rays are usually sufficient to identify a non-ossifying fibroma and to check in on its growth from time to time. If the tumor is relatively large, your healthcare provider may order a more detailed imaging test, such as an MRI or CT scan, to look at the structural integrity of the bone and check for signs of weakening.
On an X-ray, a non-ossifying fibroma is a dark mass with a white edge. Under the naked eye, it is yellow or tan in color and appears fleshy and fibrous, like scar tissue. It’s usually between 3 and 7 centimeters in size.
Most non-ossifying fibromas won’t require any treatment. If your healthcare provider is aware of the tumor, they may want to observe its growth over time. If the tumor grows big enough, even if it isn’t causing any symptoms, they may recommend removing it to avoid structural weakening of the bone.
If your child has pain or irritation at the site of the tumor, see your healthcare provider right away. They’ll analyze the cause, whether it’s the size, or a fracture, or both. They may recommend removing the tumor through surgery to relieve symptoms and preserve the growing bone.
Non-ossifying fibromas are removed through a simple surgical procedure called curettage. Surgeons scrape the tumor out of the bone with special tools. Then they’ll fill in the hole with a bone graft, either from your child’s own body or from a bone donor. Sometimes they may use a bone replacement material.
The surgery has an excellent recovery rate. Your child should be able to return to all normal activities within three to six months. Your healthcare provider will continue to take periodic X-rays to see how the bone is healing and make sure the tumor doesn’t grow back at the site. It rarely does.
Non-ossifying fibromas stop growing when the skeleton stops growing, sometime during adolescence. After that, they begin to recede on their own. Most are healed by the child’s early twenties. Occasionally, they may be seen as late as 30.
Most non-ossifying fibromas won’t cause any trouble. They rarely grow big enough to cause symptoms and tend to go away by themselves in early adulthood.
The only significant complication of a non-ossifying fibroma is weakening of the bone, which can lead to easy fracture. Your healthcare provider can help prevent this by keeping track of the tumor’s growth.
NOFs that do cause complications can be removed through surgery. Surgical patients can expect to make a full recovery. The bones of growing children heal well.
You should make sure your healthcare provider is aware of the tumor and takes X-rays from time to time to watch its growth. If your child begins to experience any symptoms, such as swelling, tenderness, or dull pain, bring them in to have the tumor and the bone looked at.
A note from Cleveland Clinic
“Non-ossifying fibroma” is a long and technical name for a condition that’s usually found by accident and shouldn't be cause for concern. It’s a small clump of cells on your child’s bone that they will probably never notice. It never spreads or turns to cancer and usually doesn’t grow very big. Your healthcare provider will keep an eye on its growth to make sure it doesn’t weaken the bone it grows on. Non-ossifying fibromas rarely require removal, but if they do, the surgery is simple. Most NOFs will heal themselves after your child is fully grown.
Last reviewed on 10/10/2021.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy