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from the American Academy of Orthopaedic Surgeons

Diseases & Conditions



Staying Healthy

Extra-Abdominal Desmoid Tumors

Extra-abdominal desmoids are deep-seated, benign (noncancerous) tumors. They are very rare tumors. While desmoid tumors do not spread to other parts of the body (metastasize), they can grow aggressively and become intertwined in surrounding tissue—making it difficult to remove them surgically. Even after apparently complete surgical removal, desmoid tumors frequently grow back.


Desmoid tumors are fibrous—much like scar tissue. Because of this, they are also called aggressive fibromatoses. The tumors can become large in size and grow aggressively into surrounding muscle, tendons, joints and even bone.

Although desmoid tumors are typically slow growing, they can grow rapidly in some instances, mimicking a malignant or cancerous process.

The tumors are most often found in the shoulder and buttock, followed by the arm, forearm, and the back of the thigh and knee.

Desmoid tumors may occur at any age, but are most likely to occur in older children and young adults up to 40 years of age. Males are affected more often than females.


The exact cause of desmoid tumors is not known.

Typically, tumors develop in just one area, although sometimes they may appear in several locations. Multiple locations of disease can be associated with familial adenomatous polyposis, a genetic abnormality in which potentially malignant polyps develop in the intestinal lining.

This supports the theory that desmoids may have a genetic cause. Other theories have been explored as well, including hormonal and traumatic causes, but there are no definitive conclusions.


Most commonly, a desmoid tumor causes a mildly painful, firm mass or lump. At times, the lesion may grow rapidly, causing pain and restricting motion in nearby joints.

Although they are rarely fatal, desmoid tumors may invade local nerves and blood vessels. This can result in pain and marked disability.

Doctor Examination

Your doctor will perform a thorough physical examination and use imaging studies and other tests to diagnose an extra-abdominal desmoid tumor.

Physical Examination

During the exam, your doctor will assess the size and consistency of the lump, as well as its effect on the overlying skin, limb length and motion of surrounding joints.


Magnetic resonance imaging (MRI) scan. An MRI provides clear images of soft tissues and can be helpful in evaluating desmoid tumors. An MRI will show the overall size and location of the tumor and whether any surrounding vital structures are involved.

MRI scan of an extra-abdominal desmoid tumor

(Left) This MRI shows an extra-abdominal desmoid tumor in the arm. (Right) This MRI shows the same tumor in a cross-section view.

Biopsy. A biopsy is necessary to confirm the diagnosis. During a biopsy, a tissue sample of the tumor is taken and examined under a microscope. The procedure is often performed in the doctor's office. Your doctor may give you a local anesthetic to numb the area and take a sample using a needle. Biopsies can also be performed as a small operation.


Extra-abdominal desmoid tumors are unpredictable. Some tumors grow at a rapid rate. Other tumors remain unchanged after diagnosis. There are even instances of spontaneous regression. This erratic behavior makes treatment challenging.

Treatment for a tumor depends upon its location and characteristics, as well as the patient's preferences.

Nonsurgical Treatment

Nonsurgical treatments have been used to treat desmoid tumors with mixed results. 

Observation.  Because some desmoid tumors grow slowly and may even shrink, the first line of treatment is usually careful observation over time. During regular visits to your doctor,  imaging studies and other tests will be used to check for changes in the tumor.

Radiation. Radiation therapy can destroy cancer cells and shrink tumors. In some cases, desmoid tumors may be treated successfully with radiation therapy alone. In other cases, radiation therapy is used in conjunction with surgery. Radiation treatments usually begin two weeks after the surgical procedure.

Radiation therapy is usually used only if the patient has reached skeletal maturity. There are risks associated with radiation, including fibrosis, skin necrosis, joint stiffness, osteonecrosis, growth plate disturbance and neurovascular damage. In some instances, radiation may actually promote growth of cancerous tumors or sarcomas.

Desmoid tumors treated with a combination of surgery and radiation or with radiation therapy alone may return.

Hormone therapy. Desmoids are known to have estrogen receptors. This means that their growth may be stimulated by the hormone estrogen. Drugs that block the hormonal stimulation of the tumor can be effective at controlling the tumor growth.

Nonsteroidal anti-inflammatory drugs (NSAIDs). Medications such as ibuprofen and naproxen, as well as a special kind of NSAID called a COX-II inhibitor, can be effective in treating desmoid tumors.

Chemotherapy. Low doses of chemotherapy drugs are effective in management of desmoids. Long-term use of these drugs is difficult, however, due to their cumulative effects in the body.

Other nonsurgical treatments. Radiofrequency ablation, in which the tumor is heated with a high-frequency electrical current, as well as direct injection of the tumor with irritating chemicals (i.e., acetic acid), have also shown some promise in treating desmoid tumors.

Surgical Treatment

In some cases, surgery to remove the tumor may be recommended. However, it can be difficult during surgery to determine the outer extent of the tumor. This is because desmoids are not well encapsulated and they often intertwine with other tissues. A tumor may recur after surgery with local rates of recurrence ranging from 25% to 68%.

Desmoids frequently invade a limb's vital nerves and blood vessels. Because of this, full removal of the tumor may impair function in the surrounding area. Limited surgery, combined with additional treatments, such as radiation or chemotherapy, may be successful in these cases.


How long it will take to return to your daily activities will vary depending on the location of the tumor and the extent of the surgical procedure.

A physical therapist will provide you with specific exercises to help strengthen your muscles. The goal of physical therapy is to help you regain function and range of motion in the affected limb and surrounding joints. Exercises can be continued at home or at a local gym.

You will continue to make follow-up visits to your doctor every three months for two years, and then in 6 to 12 month intervals. During these visits, your doctor will monitor your progress and check for tumor recurrence. He or she may order tests such as an MRI or CT scan to check your progress. If you are taking a long-term medication to treat your tumor, such as hormonal therapy or NSAIDs, your doctor may order blood tests as well.

Last Reviewed

July 2019

Contributed and/or Updated by

Rajiv Rajani, MDLindsay Hartup, BA

Peer-Reviewed by

Stuart J. Fischer, MD

AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS Find an Orthopaedist program on this website.