Copyright 2008 American Academy of Orthopaedic Surgeons
Extra-Abdominal Desmoid Tumors

Extra-abdominal desmoids are deep-seated tumors that are rare and benign, meaning they do not spread to other parts of the body (metastasize).

Desmoid tumors are also called aggressive fibromatoses. They have this name because they are fibrous, similar to scar tissue, and can grow aggressively into surrounding muscle, tendons, joints, and even bone. They can reach significant sizes. Although they are typically slow growing, desmoids can at times grow rapidly, mimicking a malignant or cancerous process.


The exact cause of desmoid tumors is not known.

Tumors generally develop in just one area, but 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 have a genetic cause, but other theories have been explored - including hormonal and traumatic causes - with no definite conclusions.


Older children and young adults up to the age of 40 are most likely to have desmoid tumors. Extra-abdominal desmoids usually occur in men and are more common in the shoulder and buttock, followed by the back of the thigh and knee, the arm, and forearm.

The most common symptom is a mildly painful, firm mass or lump in an arm or leg.

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.


A thorough physical exam is the first step in accurate diagnosis of desmoid tumors. Your doctor will assess the size and consistency of the lump, as well as its affect on the overlying skin, limb length, and motion of the surrounding joints.

A magnetic resonance imaging (MRI) scan gives your doctor information about the tumor. An MRI may show the overall size and location of the lesion and whether there is any involvement of surrounding vital structures.

A biopsy is necessary to confirm the diagnosis. During a biopsy, a tissue sample of the lesion is taken. The procedure can often be performed in the physician's office. This offers at least two advantages: the site of the incision is small and the diagnosis can be made more quickly.


Desmoid tumors are unpredictable. Some tumors grow at a rapid rate. This can cause concern for an underlying malignancy. Other tumors remain unchanged after diagnosis. There are even instances of spontaneous regression. This erratic behavior makes treatment challenging.

Treatment options vary. How a desmoid tumor is treated can depend upon the location of the tumor, its characteristics, and patient preferences.

Surgical Treatment

Surgery to remove the tumor is the preferred treatment method. However, it can be difficult during surgery to determine the limits of the tumor's reach. This is because desmoids are not well encapsulated. In other words, they can intertwine with other tissues. The tumor can return after surgery, with local rates of return ranging from 25% to 68%.

Desmoids are notorious for invading a limb's vital nerves and blood vessels. This means that full removal of the tumor may impair function in the surrounding area. In cases like these, limited surgery combined with additional treatments, such as radiation or chemotherapy, may be successful.

Nonsurgical Treatment

Nonsurgical treatment, such as radiation therapy, hormonal therapy, chemotherapy, and nonsteroidal anti-inflammatory drugs (NSAIDs), have been used to treat desmoid tumors. The results have been mixed.

  • Radiation therapy
    When full removal of the tumor would lead to major problems in function or cause disfigurement, radiation may be used in association with other treatment methods. Radiation treatments are usually started two weeks after surgery. Tumors treated with a combination of surgery and radiation may return between zero and 40% of the time, depending on the extent of disease.

    Desmoid tumors treated with radiation therapy alone may return between 12% and 31% of the time.

    Radiation therapy is used only if the skeleton has reached maturity. Complications of radiation therapy include fibrosis, skin necrosis, joint stiffness, osteonecrosis, growth plate disturbance, and neurovascular damage. In some instances, radiation may instigate growth of malignant tumors, or sarcomas.

  • Drug Treatment
    Desmoids are known to have estrogen receptors. This means that desmoid tumors may be stimulated by the hormone estrogen. Drugs that block the hormonal stimulation of the tumor are sometimes effective at controlling the tumor growth.

    NSAIDs as well as Cox II inhibitors can be effective in treating desmoid tumors.

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

    Radiofrequency ablation and direct injection of the tumor with irritating chemicals, such as acetic acid, have also shown some promise.


After surgery, rehabilitation is geared toward strengthening muscles. The goal is to regain function and range of motion in the affected limb and surrounding joints. Patients often work with a physical therapist at first, who will develop a rehabilitation and exercise program. The program can be continued at home or at a local gym. Recovery time depends on the extent of the surgical procedure.

After treatment for a desmoid tumor, patients see their doctor on a regular basis. The doctor will monitor their progress and assess local recurrence. During the follow-up visits, the doctor will examine the area and may order tests, such as MRIs and/or CTs. If a long-term medication (hormonal therapy or NSAIDs) has been prescribed to treat the tumor, blood tests may also be ordered. Follow-up visits are scheduled every three months for two years, and then in 6 to 12 month intervals.

Research On the Horizon

New research in the form of better drugs will likely be the mainstay for the treatment of desmoid tumors. Drugs such as IMATINIB show some early promise in desmoids management.

Last reviewed: April 2008
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.
Copyright 2008 American Academy of Orthopaedic Surgeons
The American Academy of Orthopaedic Surgeons
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Phone: 847.823.7186

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