Desmoid tumors

Learn about this rare type of tumor, including symptoms, diagnosis and treatment.

Update Date: 04.09.2026

Overview
Symptoms
Causes
Risk factors
Diagnosis
Treatment
Coping and support
Preparing for an appointment

Overview

Desmoid tumors are growths made of cells that form in the body's connective tissue. A desmoid tumor also may be called desmoid-type fibromatosis or aggressive fibromatosis. These rare tumors most often grow in the belly, also called the abdomen, and in the lining of the belly. Other common places are the arms and legs. But desmoid tumors may happen anywhere in the body.

Desmoid tumors are not cancer. They cannot spread to other parts of the body. But they can grow aggressively into nearby tissues and organs, causing serious issues. Because of this, people with desmoid tumors often get care from specialists who treat soft tissue tumors, including cancer specialists.

Desmoid tumors can be confused with other soft tissue tumors. A biopsy and other tests are needed to diagnose desmoid tumors.

How a desmoid tumor grows and whether it needs treatment can be hard to predict. Some grow slowly. Many may not need treatment. Others grow more quickly. A desmoid tumor can grow into nearby organs or structures and cause symptoms. Most tumors are not life-threatening. But a desmoid tumor that grows in the head or neck can sometimes cause serious health issues.

Desmoid tumors may be treated with medicine, surgery or other options.

Symptoms

Symptoms of a desmoid tumor depend on where the tumor is located. Desmoid tumors can develop anywhere in the body. Desmoid tumors most often form in the connective tissue of the wall of the belly, called the abdominal wall, arms and legs. These tumors rarely form in breast tissue.

Signs and symptoms of desmoid tumors typically include:

  • A mass or area of swelling.
  • Pain.
  • Nausea and vomiting when a desmoid tumor grows in the belly.

If the desmoid tumor is close to the skin, you may see the mass or area of swelling. It may feel firm.

When to see a doctor

Make an appointment with a doctor or other healthcare professional if you have any ongoing symptoms that worry you.

Causes

It's not clear what causes desmoid tumors.

Desmoid tumors are growths of cells that form in the connective tissue. Connective tissue surrounds and supports other structures within the body.

Desmoid tumors happen when cells in the connective tissue develop changes in their DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, DNA gives instructions for cells to grow and multiply at a set rate. The instructions also tell the cells to die at a set time. In tumor cells, the DNA changes give different instructions. The changes tell the tumor cells to make many more cells quickly. Tumor cells also can keep living when healthy cells would die. This causes too many cells within the connective tissue.

Some people notice they have a desmoid tumor after surgery or injury. Some people notice they have a desmoid tumor during or after pregnancy. It's not clear if these events lead to developing a desmoid tumor. There is no evidence that a diet or lifestyle factor causes or prevents a desmoid tumor. Diet and lifestyle also do not seem to affect tumor growth or need for treatment.

Risk factors

Anyone can develop desmoid tumors. But the risk of desmoid tumors can go up if you have a genetic syndrome that causes many colon polyps. People with a condition called familial adenomatous polyposis (FAP) have a higher risk of desmoid tumors. This genetic syndrome is caused by a genetic change that can be passed from parents to children. The inherited condition causes many growths, called polyps, in the colon. Most people with desmoid tumors do not have FAP.

Diagnosis

Tests and procedures typically used to diagnose desmoid tumors include a physical exam, imaging tests and a biopsy.

  • Physical exam. During a physical exam, a healthcare professional examines you to better understand your symptoms.
  • Imaging tests. Imaging tests make pictures of the body. They can show the location and size of a desmoid tumor. Imaging tests used to diagnose a desmoid tumor may include MRI or CT. Desmoid tumors often look solid on imaging tests. But their appearance can vary. And they can look like other types of soft tissue tumors.
  • Biopsy. A biopsy is a procedure to remove a sample of tissue for testing in a lab. For desmoid tumors, the sample typically is collected using a needle to draw out some of the tissue. Sometimes surgery may be needed to remove a tumor for testing.

In the lab, specialists in analyzing body tissues, called pathologists, look at the tissue sample to examine the types of cells in the tumor and see whether the cells are likely to be aggressive. This information helps confirm the diagnosis and guide treatment.

Treatment

Desmoid tumors can be treated with medicine, surgery, radiation therapy and ablation. If a desmoid tumor doesn't cause symptoms, treatment might not be needed. Specific treatment is based on each person's individual situation.

Watching for tumor growth

If a desmoid tumor doesn't cause symptoms, it might not need treatment. The healthcare team might watch the tumor over time, to see if it grows. Imaging tests may be done every few months to check the tumor. Some tumors never grow and may not need any treatment. Some tumors may shrink on their own without treatment. Growth seen on imaging tests doesn't always mean treatment is needed.

Medicines

Desmoid tumors that grow or cause symptoms might need treatment with medicine.

Medicines that help treat desmoid tumors include:

  • Targeted therapy. Targeted therapy uses medicines to attack specific chemicals in the tumor cells. By blocking those chemicals, targeted therapy can cause tumor cells to die. One medicine that works in this way to treat desmoid tumors is nirogacestat (Ogsiveo). This and other targeted therapy medicines help treat desmoid tumors that are growing or causing symptoms.
  • Chemotherapy. Chemotherapy treats the tumor with strong medicines. Chemotherapy might be needed when a desmoid tumor is causing serious symptoms.

Researchers also are looking into other medicines that might be useful in treating desmoid tumors. Some may be available through research studies that test new treatments. These studies are called clinical trials.

Hormone therapy, such as tamoxifen, and nonsteroidal anti-inflammatory drugs (NSAIDs), have been used to treat desmoid tumors in the past. But evidence for these older treatments is limited. Newer options now play a larger role in care.

Surgery

Surgery may be recommended when a desmoid tumor causes symptoms. It also may be recommended if medicine doesn't control the symptoms or stop tumor growth. Surgery often removes all of a desmoid tumor, along with a small amount of healthy tissue around it. But sometimes the tumor grows into nearby structures and cannot be completely removed. In those situations, surgeons may remove as much of the tumor as possible.

Radiation therapy

Radiation therapy treats the tumor with powerful energy beams. Radiation therapy may be used to treat a desmoid tumor if a person isn't healthy enough to have surgery or if treatment with medicine hasn't worked.

Ablation treatments

Cryoablation is a treatment that uses extreme cold directly on tumor cells to destroy them. During cryoablation, thin metal probes are placed into the area where the tumor is located. The probes are filled with a gas that freezes nearby tissue. Cryoablation may be used for some smaller desmoid tumors that are not located in the belly.

Other types of ablation using heat or focused energy also may be used to treat desmoid tumors.

The prognosis for desmoid tumors varies. These tumors do not spread to other parts of the body. But how they behave can be hard to predict. A tumor may grow, stay the same size or shrink without treatment. Desmoid tumors can come back after treatment.

One study followed people with desmoid tumors for five years after diagnosis. People in the study had tumors outside the belly and did not have an inherited condition that increases the risk of desmoid tumors. About 2 out of every 3 people did not need treatment during those five years, including some people with desmoid tumors that got smaller. This is called spontaneous regression. Treatment was more likely for people with larger tumors. It also was more likely for tumors in the head, neck, arms or legs than for tumors in the abdominal wall.

Desmoid tumors are hard to predict. The risk of recurrence and the need for treatment depend on many factors. Talk with your care team about how the location, size and growth of your tumor affect follow-up care and whether you may need treatment.

Coping and support

With time, you may find what helps you cope with the worries that may come with a diagnosis of a desmoid tumor. Until then, here are some ideas to help you cope.

Learn enough about desmoid tumors to make decisions about your care

Ask your healthcare team about your tumor, including your test results and treatment choices. As you learn more about desmoid tumors, you may become more confident in making treatment decisions.

Find a good listener

Finding someone who is willing to listen to you talk about your hopes and worries can be helpful as you manage your diagnosis. This could be a friend or family member. A counselor, medical social worker or clergy member also may offer helpful guidance and care.

Connect with others

Other people who've had desmoid tumors may be able to offer you support and insight because they understand what you're experiencing. Ask a member of your healthcare team to help you connect with others through support groups in your community. Find support online through Mayo Clinic Connect, which is a community where you can connect with others for support, practical information and answers to everyday questions.

Preparing for an appointment

Make an appointment with a doctor or other healthcare professional if you have any symptoms that worry you. If your healthcare professional suspects that you might have a desmoid tumor, you may be referred to a doctor who specializes in treating cancer, called an oncologist.

Here's some information to help you get ready for your appointment.

What you can do

  • Be aware of anything you need to do before the appointment. When you make the appointment, ask if there's anything you need to do beforehand, such as not eating or drinking for a certain amount of time.
  • Write down the symptoms you're having. Include any that may not seem related to the reason for which you scheduled the appointment.
  • Write down key medical information, including medical conditions and surgeries that you've had.
  • Make a list of all medicines, vitamins or supplements you're taking and the doses.
  • Take a family member or friend along, if possible. Sometimes it can be hard to remember all the information provided during an appointment. Someone who goes with you may remember something that you missed or forgot.
  • Write down questions to ask your healthcare team.

For desmoid tumors, some basic questions to ask your healthcare professional include:

  • What most likely is causing my symptoms?
  • Are there other possible causes for my symptoms?
  • What tests do I need?
  • What are my treatment options?
  • What are the potential side effects of each treatment option?
  • I have other health conditions. How can I best manage them together?
  • Should I see a specialist?
  • Are there brochures or other printed materials I can take with me? What websites do you recommend?

Be sure to ask any other questions you may have.

What to expect from your doctor

Your healthcare professional is likely to ask you several questions, such as:

  • When did your symptoms begin?
  • Are your symptoms always present, or do they come and go?
  • How severe are your symptoms?
  • What, if anything, makes your symptoms better?
  • What, if anything, makes your symptoms worse?

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