Desmoid tumors are noncancerous growths that form in the body’s soft tissues. These are rare tumors — between 900 to 1,500 people are diagnosed with them in the U.S. each year.

If you or a loved one has recently been diagnosed with a desmoid tumor, you’re likely left with plenty of questions. In this article, we’ll discuss five things to know about desmoid tumors. We’ll cover their symptoms, causes, diagnosis, and treatment.

1. Symptoms Depend on a Tumor’s Location

Desmoid tumors can form in several parts of the body. Doctors classify desmoid tumors as:

• Abdominal or intra-abdominal — Affecting the tissues supporting the intestines in your abdomen
• Extra-abdominal — Affecting the soft tissues outside your abdomen in the arms, legs, or chest

Some people with desmoid tumors don’t experience any symptoms. In fact, they may not even know they have any tumors until they have imaging scans done for an unrelated reason. Other people can experience symptoms that interfere with their day-to-day life. The types of symptoms you may have depend on where desmoid tumors are in your body.

Abdominal and intra-abdominal symptoms are associated with tumors growing on or in the abdominal wall or within the abdomen. You likely won’t notice anything out of the ordinary unless the tumors begin pressing on your organs. At that point, you may feel a mass or lump when you press on your stomach.

Other signs and symptoms of intra-abdominal tumors may include:

• Nausea and vomiting
• Bloating
• Cramping
• Weight loss
• Cachexia, or loss of fat and muscle due to metabolism problems
• Constipation
• Holes in your intestines (intestinal ruptures)

Extra-abdominal tumors form lumps in the arms, legs, neck, or chest. These tumors begin growing within deep spaces and tissues inside the body. Eventually, they begin pushing your healthy tissues out of the way. Many people with desmoid tumors experience pain, soreness, and discomfort from tumors pressing on muscles, nerves, and blood vessels.

Other symptoms of extra-abdominal desmoid tumors may include:

• Problems moving due to muscle, nerve, and bone damage from tumors
• Insomnia or difficulty sleeping
• Nerve pain or a “pins and needles” sensation

2. Most Desmoid Tumors Have No Clear Cause

In most cases, desmoid tumors occur randomly and have no clear cause. These tumors are also described as “sporadic.” Most people with desmoid tumors have mutations or changes in the catenin beta 1 (CTNNB1) gene. About 85 percent of sporadic desmoid tumors have mutations in this gene.

About 5 percent to 10 percent of people with desmoid tumors also have familial adenomatous polyposis (FAP). This is a genetic condition passed down through family members. FAP is associated with mutations in the adenomatous polyposis coli (APC) gene. People with Gardner syndrome (a type of FAP) seem to have a higher risk of desmoid tumors.

Surgery and injuries are also associated with desmoid tumors. People with CTNNB1 mutations make too much beta-catenin — a protein involved in wound healing. Beta-catenin tells the cells in scar tissue to keep growing and dividing, leading to tumor formation.

People who are pregnant or have recently given birth may also develop desmoid tumors. Doctors and researchers believe this is due to high estrogen levels and injury to the abdomen.

3. Doctors Use Imaging Tests and Biopsies To Diagnose Desmoid Tumors

There’s currently no single test used to confirm a desmoid tumor diagnosis. Instead, your doctor will use a combination of tests to find out what’s causing your symptoms. At your physical exam, your doctor will check your body for any masses or lumps. They’ll also ask about your recent symptoms and medical history.

Imaging tests are used to take detailed pictures of your body to look for desmoid tumors. Magnetic resonance imaging (MRI) is a common imaging test for diagnosing desmoid tumors. Computed tomography (CT) scans can also be used, but they carry a risk of radiation exposure and also aren’t safe during pregnancy. For this reason, MRI is preferred.

Your doctor will use your imaging test results to find the best place to take a tissue sample (biopsy). A biopsy is the only way to confirm you have desmoid tumors. A pathologist (tissue specialist) will look at the sample under a microscope for any tumor cells.

Your doctor may also suggest genetic testing to see if your desmoid tumors are caused by a specific mutation.

4. Not All Desmoid Tumors Require Treatment

Every person’s desmoid tumor diagnosis is unique and requires a different treatment plan. You’ll work together with your care team to find the treatment or combination of treatments that is best for you.

Your care team should include sarcoma specialists. These are oncologists who specialize in treating sarcomas. Sarcomas are rare cancers that form in the same parts of the body as desmoid tumors, primarily the connective tissue. Although desmoid tumors are not cancer, a sarcoma specialist is best prepared to help you treat them.

Active Surveillance

Some people don’t need desmoid tumor treatment right away. Instead, their doctors place them on active surveillance, or watchful waiting, to monitor their condition. They’ll have imaging scans to see how their tumor grows over time. Some people have slow-growing tumors that never get big enough to need treatment. Others may see a complete regression or disappearance of their tumors without treatment.

Surgery

Surgery is no longer recommended as the first treatment option because desmoid tumors can still return afterward. Your health care team may suggest surgery for tumors in certain locations. For example, small tumors in the abdominal wall may be removed, as they have a lower chance of recurrence.

Chemotherapy

Chemotherapy uses medication to kill cancer cells and shrink tumors. Your health care team may suggest chemotherapy to treat an aggressive tumor affecting your organs or causing other health problems.

Radiation

Radiation therapy uses concentrated X-ray beams to damage desmoid tumor cells. Like surgery, radiation therapy isn’t usually given as a first treatment option because it carries a remote risk of secondary cancers. Your doctors may recommend this treatment if your desmoid tumors don’t respond well to other treatments.

Targeted Therapies

Targeted therapies specifically “target” or block proteins in desmoid tumor cells. The U.S. Food and Drug Administration (FDA) has approved the drug nirogacestat (Ogsiveo) for treating desmoid tumors. Your doctor may also prescribe other drugs known as tyrosine kinase inhibitors to stop tumors from growing.

Other Treatments

Studies show that desmoid tumors use the hormone estrogen to grow. For this reason, hormonal therapies like tamoxifen have been used to slow the growth of desmoid tumors. Recently, this type of treatment has stopped being recommended due to a lack of sufficient evidence that it is effective.

Nonsteroidal anti-inflammatory drugs (NSAIDs) can be used to treat pain associated with desmoid tumors. NSAIDs are no longer recommended for shrinking tumors.

Ablation uses a thin probe to deliver a treatment directly into a desmoid tumor. One example is cryoablation, which freezes the tumor.

Follow-Up Care

After you complete treatment, you will receive follow-up care to monitor your health. Your doctors will examine you, and they may also order more imaging tests. Follow-up care is important to check if a desmoid tumor has returned or if a tumor has grown. You may require additional treatment if your tumor has progressed or returned.

5. Desmoid Tumors Can Return After Treatment

Overall, researchers have found that desmoid tumors are rarely a cause of death. Since desmoid tumors are so rare in general, studies haven’t determined an accurate survival rate yet.

One study of 94 children and teenagers from Italy found that the overall five-year survival rate with desmoid tumors was 99 percent. This means that after five years, 99 percent of the study participants were still alive.

There’s also a chance that your desmoid tumors can return after completing treatment. This is especially true with surgery. Study results have varied, but research shows tumors grow back for between 20 percent and 80 percent of people who have had surgery to remove them. If you’re concerned about your desmoid tumors returning, talk to your doctor about your treatment plan.

Talk With Others Who Understand

MyDesmoidTumorTeam is the social network for people with desmoid tumors and their loved ones. On MyDesmoidTumorTeam, members come together to ask questions, give advice, and share their stories with others who understand life with desmoid tumors.

Are you or a loved one living with a desmoid tumor? Share your experience in the comments below, or start a conversation by posting on your Activities page.