What Is a Desmoid Tumor?

Desmoid tumors, otherwise known as aggressive fibromatosis or desmoid-type fibromatosis, are a rare type of a benign connective tumor. They typically affect young adults in their 20s and 30s, but they can occur at any age. They are benign (noncancerous) masses of fibroblast cells and are most often found in the:

• Abdomen 
• Shoulders
• Upper arms
• Thighs

Fibroblast cells make up the connective tissue that supports bones, ligaments, tissues, and muscles. These cells also help hold the body’s organs in place and assist in healing wounds. 

This article will discuss symptoms, possible causes, diagnosis, treatments, and prognosis of desmoid tumors.

Desmoid Tumor Symptoms

Symptoms of desmoid tumors vary and are dependent on the stage, location, and extent of invasion of the nearby tissues. Not all people with these tumors have noticeable symptoms. 

While each case is unique, there are a few common symptoms, including:

• Pain: A desmoid tumor in the early stages of growth may appear as a painless lump under the skin. However, the most common symptom is pain. Those that grow in the abdomen may not be noticeable until the tumor starts pressing on an organ and causes discomfort.  
• Tingling: This feeling of “pins and needles” happens when the tumor presses on nerves or blood vessels.
• Swelling: Swelling usually occurs in the tumor area, such as the arm or leg, and may worsen at night. 
• Sleep loss: Loss of sleep may occur due to discomfort, pain, tingling, or swelling. 
• Decreased mobility: Decreased mobility includes limping or difficulty moving the arms, hands, legs, or feet. 
• Gastrointestinal issues: Bloating, constipation, or abdominal pain due to a blocked bowel can also be symptoms of a desmoid tumor in the abdomen.

If you have any of these symptoms, please make an appointment with your doctor.

Causes

While the exact cause of all desmoid tumors is unknown, studies have found that there are genetic mutations within fibroblast cells that cause abnormal growth.

These cells have deoxyribonucleic acid (DNA), or genetic makeup, that gives them instructions. In desmoid tumors, the DNA of the fibroblast cells make too much of a protein called beta-catenin. The excess protein stimulates the cells to accumulate into a mass when they usually wouldn’t.

There is a correlation between desmoid tumors and familial adenomatous polyposis (FAP). People with FAP, also called Gardner syndrome, have a higher risk of developing desmoid tumors and colon cancer.  

FAP is hard to detect, so patients with desmoid tumors often have a colonoscopy to rule out FAP.

Diagnosis

Masses or growths that are painful or painless but larger than a golf ball need further evaluation by a healthcare provider. Tests and procedures used to diagnose these types of lumps or masses include:

• Physical exam: The doctor will examine the area surrounding the lump or where there is discomfort. 
• Imaging tests: The healthcare provider may order an imaging test such as an X-ray, computed tomography (CT), magnetic resonance imaging (MRI), bone scan, or positron emission tomography (PET) scan.  
• Biopsy: A biopsy is a tissue sample of the lump used to gain a definitive diagnosis. The doctor may use a local anesthetic (numbing medication) or general anesthesia to minimize discomfort. The tissue sample is reviewed in the lab by pathologists, doctors who examine body tissues under the microscope.  

Treatment

Desmoid tumors are benign (noncancerous) rather than malignant (cancerous) because they do not travel to other body parts. Some grow slowly and don't require immediate treatment. However, aggressive tumors that invade nearby tissues may need to be treated by an oncologist, a doctor who specializes in cancer. 

After a definitive diagnosis is confirmed, the healthcare team will develop a treatment plan. 

Initial treatments may include active surveillance and supportive care. However, more aggressive tumors may require a combination of interventions such as surgery, radiation, chemotherapy, or other medications.

Active Surveillance

In the past, surgery was considered first as the treatment of choice for a desmoid tumor. However, active surveillance, or a “wait and see” strategy, may also be appropriate.   

The healthcare team may monitor the tumor to see if it grows or starts to cause more symptoms. They often perform imaging or other diagnostic tests every few months while monitoring the desmoid tumor. While some tumors never grow and some may shrink on their own, almost half of them will eventually need surgery.

Supportive Care

If the patient is experiencing symptoms, supportive care (symptom relief) will most likely be the first step in treatment. Both pharmacological (medication) and nonpharmacological (nonmedication) therapies can help treat symptoms of a desmoid tumor.  

If a desmoid tumor becomes more aggressive, a team of oncologists will work closely together to develop a treatment plan. The treatment for aggressive tumors may include one or a combination of the following:

Surgery

This option involves an operation performed under general anesthesia. The surgeon will remove all of the tumor, including a small margin of healthy tissue surrounding it. If the tumor intertwines with surrounding tissues, ligaments, tendons, or organs, the surgeon will remove as much of the tumor as possible.

Radiation Therapy

Radiation therapy, including gamma knife and proton beam therapy, is used to kill tumor cells. Healthcare teams often use radiation when a patient is not healthy enough for surgery or when the tumor is in a high-risk area. Radiation may also be used in combination with surgery to decrease the risk of the tumor returning. 

Chemotherapy

While desmoid tumors are not cancer, oncologists may still prescribe chemotherapy medications to kill tumor cells. They often consider this treatment if the tumor is growing quickly and surgery isn't an option.  

Medications

Hormone therapy, anti-inflammatory drugs, and tyrosine kinase inhibitors (TKIs) such as Sorafenib may be included in the treatment plan.

Prognosis

Desmoid tumors rarely cause death. However, aggressive tumors can destroy vital organs and structures surrounding them. Early detection and treatment are critical in delaying their growth. 

Symptoms, complications, and quality of life depend on the tumor’s location, how fast it grows, and treatment success. Patients need to be monitored closely by their healthcare team to decrease the risks of complications and achieve symptom management.  

Coping

Being diagnosed with a rare tumor can cause uncertainty, discomfort, and stress. If you or a loved one has been diagnosed with a desmoid tumor or you're waiting for answers, you most likely have multiple questions and concerns at the same time. Here are a few coping strategies you can try:

• Gather information: Learning as much as you can about the condition, diagnostic tests, and treatment options will help you be more confident about decisions regarding your care.  
• Identify your support system: Friends and family can provide a great support system both emotionally and practically. If someone offers to clean your house, babysit your children, or bring you a meal, please consider accepting the help. 
• Talk about it: Find someone you trust to be a good listener. This can be a friend, family member, counselor, chaplain, or support group.  
• Find a support group: Ask your healthcare team if they know of any support groups in the area or on the Internet. These can be beneficial because members are in the same situation as you are and understand the struggles of the condition. They can also provide practical support from experience. 

A Word From Verywell

We understand that having any of these symptoms can be frightening. If you are concerned, make an appointment with your doctor to rule out any suspicions.  

Your doctor will want to examine you first and possibly send you for further testing or refer you to an oncologist.  

Waiting for an appointment can be stressful. It can be helpful to prepare for the appointment by gathering the following information:

• Medication list: This should include over-the-counter medications, vitamins, or other supplements you take. Include the doses and how often you take them. 
• Signs and symptoms: Prepare a list of signs and symptoms that you are concerned about. Include any that may seem unrelated.
• Medical history: This is especially important if you are seeing a new healthcare provider.
• Questions: Write a list of questions and concerns you have for your healthcare team.

As stressful as this situation may seem, remember that your healthcare team will develop a treatment strategy specifically for you. Continue to communicate with your doctor to make sure they know about any changes or concerns you might have. They can then reevaluate the situation, and you can decide together if a new course of treatment is needed.