Desmoid Tumour

Desmoid tumours are rare, noncancerous growths that develop in connective tissue throughout the body. Although they don’t spread like cancer, they can grow aggressively into nearby structures, causing pain and serious health problems.

Table of contents

• What is a desmoid tumour?
• Medical identification codes
• Other names for this condition
• How common are desmoid tumours?
• Where desmoid tumours develop
• What causes desmoid tumours?
• Who is at higher risk?
• Signs and symptoms
• How desmoid tumours are diagnosed
• Treatment approaches
• Risk of tumour return
• Healthcare professionals involved in care
• Living with desmoid tumours

What is a desmoid tumour?

Desmoid tumours are abnormal growths that arise from connective tissue, which is the tissue that provides strength and flexibility to structures such as bones, ligaments, and muscles^[1]. These tumours are made up of cells called fibroblasts, which normally help protect vital organs and play a critical role in wound healing^[3].

Desmoid tumours are considered benign, meaning they are noncancerous because they do not spread to other parts of the body (a process called metastasis)^[1]. However, they can be very aggressive locally, meaning they can invade and damage nearby tissue and organs^[2]. This aggressive behaviour is why people with desmoid tumours are often cared for by cancer doctors^[1].

The World Health Organization classifies desmoid tumours as intermediate (locally aggressive) tumours^[4]. This means they sit somewhere between completely harmless growths and true cancers. While they cannot spread throughout the body, they can grow into vital organs such as intestines, kidneys, lungs, blood vessels, or nerves, leading to pain, life-threatening problems, or rarely, death^[4].

The condition is characterized by a variable and often unpredictable course^[4]. Some desmoid tumours grow very slowly or even shrink on their own, while others grow quickly and cause serious complications^[3].

Medical identification codes

D48.1

Other names for this condition

aggressive fibromatosis, desmoid-type fibromatosis, deep fibromatosis, musculoaponeurotic fibromatosis

How common are desmoid tumours?

Desmoid tumours are rare, affecting an estimated 2 to 6 people per 1 million worldwide each year^[3]. In the United States, approximately 1,000 to 1,650 new cases are diagnosed per year^[5].

For reasons that are unclear, women develop desmoid tumours more often than men, accounting for about 70 percent of cases^[9]. Women are diagnosed 2 to 3 times more frequently than men^[5]. Most people are diagnosed in young adulthood, with the majority between ages 20 and 44^[5]. More specifically, desmoid tumours most commonly occur in people between ages 30 and 40^[2], though they can develop anytime between adolescence and late adulthood^[9].

Only 3% of soft tissue tumours are desmoid tumours, making them a very rare tumour type^[5].

Where desmoid tumours develop

A desmoid tumour can occur anywhere in the body since connective tissue is found throughout^[3]. However, they most often develop in certain areas.

Desmoid tumours are commonly found in the abdomen, arms, legs, shoulders, and upper thighs^[1][3]. They can also affect the chest wall, and less commonly, the head and neck^[2].

There are three main types based on location^[2]:

• Abdominal wall desmoid tumours: These affect the wall of tissue that surrounds organs in the belly, like the stomach
• Intra-abdominal desmoid tumours: These grow in the mesentery, the tissue that surrounds the intestines
• Extra-abdominal desmoid tumours: These develop in places other than the belly and abdominal wall, usually in the shoulders, upper arms, chest wall and upper legs, but can also affect the head and neck

Most people typically develop a single tumour, although some have multiple tumours^[9].

What causes desmoid tumours?

The exact cause of desmoid tumours is unknown^[7]. Doctors know these tumours form when a connective tissue cell develops changes in its DNA^[1]. A cell’s DNA contains the instructions that tell a cell what to do. The changes tell the connective tissue cell to multiply rapidly, creating a mass of cells that can invade and destroy healthy body tissue^[1].

Researchers have found that changes (called mutations) in two specific genes are involved in most desmoid tumours^[9]. Mutations in the CTNNB1 gene account for around 90 percent of sporadic desmoid tumours (those not inherited)^[9]. Mutations in the APC gene cause the desmoid tumours that are associated with a hereditary condition called familial adenomatous polyposis (FAP)^[9].

Both genes are involved in an important cell signalling pathway that controls the growth and division of cells. When these genes are mutated, they lead to an abnormal build-up of a protein called beta-catenin in cells, which promotes uncontrolled cell growth and the formation of desmoid tumours^[9].

Most cases are sporadic, meaning they occur randomly without a family history^[4].

Who is at higher risk?

Several factors may increase the risk of developing desmoid tumours^[2][9]:

• Younger age: Most people diagnosed are between ages 30 and 40, though they can occur anytime between adolescence and late adulthood
• Being female: Women are more likely to be diagnosed with desmoid tumours, but men are at risk as well. Often, females are diagnosed during pregnancy or shortly after, with tumours usually in the abdominal wall. Since estrogen levels are high during pregnancy, some experts believe there’s a connection between high estrogen and desmoid tumours
• Having familial adenomatous polyposis (FAP): About 5% to 10% of people with FAP develop desmoid tumours. The tumours usually arise where there was previous surgery to remove a colon polyp. Approximately 10% to 30% of people with an inherited form of colon cancer called FAP develop desmoid tumours^[9]
• Trauma or injury: Research shows having a serious injury or being repeatedly injured in the same place on the body increases the risk. There is a tendency for recurrence in the setting of prior surgery; in one study, two-thirds of patients with desmoid tumours had a history of prior abdominal surgery^[4]

In 5% to 10% of cases, desmoid tumours may run in families^[3].

Signs and symptoms

Desmoid tumour symptoms differ based on where the tumours occur^[1]. Some people with desmoid tumours have symptoms, while others do not^[3]. Many people with desmoid tumours don’t have symptoms at all, and these tumours can be discovered if the person has an imaging test for another reason^[3].

When symptoms do occur, they are usually caused by the tumour getting big enough to press on nerves or nearby organs^[2]. In general, signs and symptoms may include^[1][2]:

• A mass or area of swelling, usually in the arms, legs or belly
• Pain or a tingling sensation from a tumour pressing on nearby nerves, organs or blood vessels
• Loss of function in the affected area
• Trouble moving the arm or leg
• Cramping and nausea, when desmoid tumours occur in the abdomen

Symptoms can vary based on tumour location. For example^[5]:

• A tumour within the abdominal area may cause digestive system blockages, pain, malaise, abdominal swelling, weight loss, or muscle wasting
• Tumours in the arms or legs may cause limited movement, deformity, pain, tiredness, weakness or muscle problems

Not every lump or bump is a desmoid tumour, but you should talk to a healthcare provider if you have a lump or bump that’s larger than 2 inches, keeps getting bigger or hurts^[2].

How desmoid tumours are diagnosed

Your healthcare provider will do a physical exam and ask you about your symptoms and your medical and family history^[2][5]. They may recommend several tests:

Imaging tests: The most common imaging tests used are CT scans and MRI scans^[2][3]. These tests allow providers to see the tumour inside the body and help determine the location and size of the tumour^[5]. Ultrasound may also be used^[3]. The images may give your doctor clues about your diagnosis^[1].

Biopsy: To check if the tumour is a desmoid tumour, your doctor will do a biopsy, taking a small amount of the tumour out with a needle or with surgery, depending on your particular situation^[1][3]. This is the only way to confirm the type of tumour^[2]. A doctor trained in analyzing body tissues (called a pathologist) will study the cells under the microscope to see what kind of tumour it is and determine whether the cells are likely to be aggressive^[1][3]. This information helps guide treatment.

Depending on the tumour’s location, it may be difficult for the doctor to take a biopsy^[3].

You may need more tests if your provider thinks you may have familial adenomatous polyposis. Most people with desmoid tumours don’t have this condition. But if you do, it’s important to know since people with FAP are at increased risk of colon cancer^[2].

Treatment approaches

There is no standard approach to treating desmoid tumours; managing them is challenging and requires discussion at a multidisciplinary tumour board^[7]. Treatment for each patient will be unique, so you should go to an expert in sarcoma treatment to decide the best approach for your tumour^[3].

In 2020, an international team of experts working in the field of desmoid tumours published evidence-based, consensus guidelines for medical treatment. These guidelines recommend active surveillance as the primary approach, with other treatments considered when tumours are progressive or symptomatic^[14].

Treatment options may include^[3][11]:

Active surveillance (watch and wait): If your desmoid tumour causes no signs or symptoms, your doctor may recommend monitoring the tumour to see if it grows^[11]. You may undergo imaging tests every few months. Desmoid tumours can be hard to predict. They can shrink and go away on their own, they can remain the same size, or they can grow quickly^[3]. Some tumours never grow and may never require treatment. About 20% can regress spontaneously^[7].

Systemic therapies (medications): Medical therapies are recommended as second-line treatments for tumours at most sites that are failing observation^[14]. In November 2023, the U.S. Food and Drug Administration (FDA) approved the first drug specifically for desmoid tumours, called nirogacestat^[12]. This medication is a gamma secretase inhibitor that is indicated for adults with progressing tumours who require systemic treatment^[12]. Other medications that may be used include chemotherapy, antiestrogens, and prostaglandin inhibitors^[12].

Surgery: Surgery is generally not considered a first-line treatment option for desmoid tumours, except in certain situations if agreed upon by a multidisciplinary tumour board^[15]. If your desmoid tumour causes signs and symptoms, your doctor may recommend an operation to remove the entire tumour and a small margin of healthy tissue that surrounds it^[11]. Sometimes the tumour grows to involve nearby structures and can’t be completely removed. In these cases, surgeons may remove as much of the tumour as possible^[11]. Surgery has fallen out of favour due to high rates of recurrence^[7].

Radiation therapy: Radiation therapy may be used as a treatment for recurrent disease or as primary therapy to avoid mutilating surgical resection^[12]. It may be used postoperatively, preoperatively, or as the sole treatment^[12]. Given that radiation therapy can cause other cancers in the future, it is important to discuss alternatives with your doctor^[3].

Other treatments: Other options that can be considered include local ablative treatments such as cryotherapy (using cold) or ablation with heat or ultrasound^[14].

Pain control is paramount to improve quality of life, independently of the use of active treatment against the disease^[14]. Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used to help manage pain from desmoid tumours^[17].

Risk of tumour return

Often, desmoid tumours come back (recur) after treatment^[2]. Desmoid tumours can be difficult to completely remove with surgery^[3]. Despite surgical resection, desmoid tumours have a high rate of local recurrence^[7].

Although they do not spread throughout the body, desmoid tumours are associated with local recurrence rates ranging from 24% to 77% after surgical resection, regardless of margin status^[15]. Up to 77% of desmoid tumours may recur after surgery, based on the tumour location and other factors^[5].

The risk of desmoid tumours returning remains high even with clean margins: various independent studies report desmoid tumour recurrence rates after complete surgical resection of 15% to 30%^[15]. Some studies suggest that the majority of tumours recur within 5 years^[15].

Factors associated with local recurrence after surgery include tumour location, age of the person, tumour size, margin status, and prior recurrence^[15].

Healthcare professionals involved in care

The National Comprehensive Cancer Network Guidelines and the Desmoid Tumour Working Group Guideline recommend an initial evaluation and management by a multidisciplinary team with expertise and experience in desmoid tumours^[15].

When diagnosed with a desmoid tumour, it is important to be evaluated and treated by a desmoid tumour expert, often known as a sarcoma specialist^[19]. Your care team may include desmoid tumour specialists, such as^[5]:

• Medical oncologist
• Surgeon, orthopedic surgeon, or surgical oncologist
• Radiation oncologist
• Pathologist
• Radiologist

Sarcoma specialists can typically be found at major sarcoma centres within academic medical centres and can help support patient care through a robust multidisciplinary team of doctors knowledgeable in medical oncology, surgical oncology, radiology, interventional radiology, pathology, and other specialties^[19].

Consulting with desmoid tumour experts can help support more accurate patient assessment, the prompt initiation of treatment when appropriate, and individualized management of symptoms^[15].

Living with desmoid tumours

Living with desmoid tumours can take a toll on your quality of life. The condition can cause anxiety about body image and how others may perceive you^[17]. Desmoid tumours can also impact your ability to work, perform daily tasks, fulfill family responsibilities, and do activities you enjoy, all of which can severely affect your mental health and how you feel about yourself^[17].

Research shows that people with this rare disease experience emotional distress that can impact self-esteem at twice the rate of those with some types of malignant (spreading) cancers^[17].

It’s important to know if your tumour is progressing, or getting worse. Signs of progression may include changes in imaging tests (the tumour may appear bigger on a CT scan or MRI) and new or changing symptoms (you may experience new symptoms, or your existing symptoms may worsen)^[5]. Regularly monitoring your symptoms and reporting them to your healthcare providers may help them create a more personalized treatment plan^[5].

Building a support network is crucial. Make sure you seek out people to help and support you. You’ll likely need emotional support as well as practical support for yourself and your family^[17]. Reach out to friends and family, your religious community, or support groups.

Mental health resources are also important. When you’re living with a rare condition like desmoid tumours, you may feel isolated, anxious, or depressed. Your oncologist or sarcoma specialist may refer you to a social worker who can connect you with more support^[17].

Learning as much as you can about desmoid tumours will help ensure that you are getting the best care and treatment possible^[19]. You are your best advocate.