Desmoid tumor

A desmoid tumor is a benign (noncancerous) growth that starts in the soft tissues. These tumors can be found across the body, rarely in more than one place at a time. Desmoid tumors are also called aggressive fibromatosis, desmoid fibromatosis, and desmoid-type fibromatosis.

Desmoid tumors do not metastasize (spread) to other areas of the body. Some desmoid tumors don’t grow or grow slowly, without causing problems. Rarely, they may even shrink or disappear on their own.

Sometimes desmoid tumors grow more quickly. They can affect nerves, blood vessels, muscles, and tendons, or block the intestines. These changes are rarely life-threatening, but they can affect quality of life.

Desmoid tumors are rare, with just 900 to 1,500 cases diagnosed in the U.S. annually. Doctors find most cases in the abdomen (belly), arms and legs, and chest in people ages 15 to 60. Among adults, women are more affected than men.

Even though they’re not cancerous, desmoid tumors are cared for by sarcoma specialists at Penn Medicine because of their similar locations, growth patterns and effective medical treatments. The Sarcoma Program at Penn Medicine’s Abramson Cancer Center has one of the nation’s most experienced desmoid tumor treatment teams.

Many desmoid tumors don’t cause any problems in early stages. Even if they grow larger, they often push healthy tissues out of the way without causing symptoms.

Larger and more invasive tumors may cause noticeable signs, including:

• Intestinal pain, bloating, constipation, or punctures
• Noticeable lump
• Pain or soreness
• Swelling
• Tingling or feeling of “pins and needles”

Doctors don’t always know what causes desmoid fibromatosis tumors. Certain factors may increase your risk of developing one:

• Family genetics: About 30 percent of people with an inherited condition called familial adenomatous polyposis (FAP) eventually develop a desmoid tumor. These cases represent 5 percent to 10 percent of desmoid tumor cases. They typically occur in the abdomen. FAP also causes polyposis, or an unusual number of polyps, in the colon and rectum. These growths can turn cancerous.
• Injury: Some desmoid tumors develop at the location of previous injuries or other traumas such as surgeries. In the breast, some desmoid tumors appear to have ties to previous implants or other operations.
• Pregnancy and contraceptive use: Desmoid tumors occur more often during pregnancy and after delivery. Researchers think this may be related to changes to the abdominal wall during pregnancy and the postpartum period as well as a potential connection to the hormone estrogen. Existing desmoid tumors can shrink when menopause starts, and some tumors do respond to hormone therapy. In addition, estrogen-based birth control appears to increase desmoid tumor risk.

Imaging tests such as magnetic resonance imaging (MRI) can help our team spot desmoid tumors. These growths look like dense scar tissue. Scans can also help determine the size of the tumor and whether it has invaded other structures.

To confirm a diagnosis, we need to take a sample of the tumor by performing an image-guided needle biopsy. A specialized pathologist studies the sample under a microscope and runs lab tests on it.

If test results and your family history point to the possibility of familial adenomatous polyposis, our team can offer genetic testing to confirm the condition.

Many desmoid tumors don’t need treatment in early stages or if they are not growing or causing pain. If the tumor causes pain or is growing quickly, our team may recommend therapies similar to cancer treatments. Your case may be discussed at a meeting of collaborative specialists called a tumor board. At Penn Medicine, the Sarcoma Tumor Board meets regularly to create treatment plans for people with desmoid tumors.

When recommending treatment, our medical team considers the tumor’s location, size, and growth rate. We also discuss what health threats the tumor is causing or could cause if it continues to grow. We weigh those aspects against the risks of treatment and prioritize your preferences.

Recommendations may include:

• Watchful waiting: Tumors that are smaller, slow-growing, painless, or otherwise not causing problems may not need immediate treatment. Instead, you will have regular appointments with your care team to monitor the tumor and watch for any changes. If the tumor grows or changes, you may start treatment.
• Targeted therapy: Newer, approved drugs such as pazopanib and sorafenib take aim at cellular pathways desmoid tumors use to grow and may provide a way to avoid surgery. Emerging drugs in clinical trials have shown even greater effectiveness and may soon be available.
• Ablation: Our doctors may recommend treatment with radiofrequency ablation (extreme heat) or cryoablation (extreme cold) to destroy the tissue of smaller tumors.
• Surgery: While medical therapy is now the main treatment for desmoid tumors, we may recommend surgical removal in rare circumstances. For surgery to be effective, tumors must be smaller and easily removable with a buffer of normal surrounding tissue. Like sarcoma surgery, these operations require specialized expertise. If all tumor tissue is not removed, the tumor can regrow, and possibly become more aggressive. Any surgery also comes with the risk of complications. For these reasons, we may first consider other methods for safe and effective tumor control.
• Radiation therapy: Radiation therapy can slow tumor growth or minimize the risk of the tumor returning after surgery. However, we use it less frequently because of its possible side effects, including damage to nearby healthy tissue.
• Chemotherapy: Drugs aimed at rapidly dividing cells can potentially shrink desmoid tumors that pose serious health risks.
• Hormonal therapy: Some desmoid tumors seem to respond to medications such as tamoxifen that stop the hormone estrogen from reaching cells.
• Non-steroidal anti-inflammatory drugs (NSAIDs): These prescription and over-the-counter drugs may slowly shrink a tumor and relieve pain and swelling. Our doctors may recommend them alone or with other therapies.