A tumor is a growth of tissue that happens when cells in your body grow and divide at a faster rate than they would normally. When we think of tumors, we often think of cancer. However, not all tumors are malignant (cancerous).

A desmoid tumor is a type of benign (noncancerous) tumor that forms from connective tissue. These types of tumors can be found in many places throughout the body, including the wall of your abdomen.

Continue reading to learn more about these tumors, what symptoms they cause, and how they’re treated.

A desmoid tumor is a type of benign tumor that originates from connective tissue. Connective tissue is the type of tissue that helps to hold your organs in place and provides support for your muscles, bones, and ligaments.

Desmoid tumors do not metastasize, meaning that they cannot spread to other areas of the body. However, they can still grow into surrounding tissue. This can lead to potentially serious complications and make them harder to remove.

There are three types of desmoid tumors. These are classified by where in the body the tumor begins.

  1. Abdominal tumor. An abdominal desmoid tumor is one that forms in your abdominal wall. The abdominal wall includes the tissues that enclose your abdominal cavity, in which many of your internal organs are located.
  2. Intra-abdominal tumor. These desmoid tumors form in the tissue connecting the organs within the abdominal cavity.
  3. Extra-abdominal tumor. These desmoid tumors occur in connective tissue found in other areas, such as the shoulders, upper arms, and thighs

As a whole, desmoid tumors are rare, affecting only 2 to 4 individuals per 1 million people and accounting for only 0.03 percent of all tumors. It’s estimated that 37 to 50 percent of desmoid tumors begin in the abdominal area.

The symptoms that you experience with an abdominal desmoid tumor can vary depending on such factors as:

  • the size of the tumor
  • where exactly it’s located
  • how fast it’s growing

If you have an abdominal desmoid tumor, you may notice a swelling or lump on your abdomen. This lump typically feels firm and can sometimes be painless.

However, as the tumor grows, it can begin to affect surrounding tissues, such as muscles and nerves. When this happens, an abdominal desmoid tumor can become very painful. This can interfere with sleep and other daily activities.

Additional symptoms of abdominal desmoid tumors typically arise due to complications, which can be potentially serious. See below for more information on potential complications.

Complications of an abdominal desmoid tumor happen when tumors grow into and disrupt nearby tissues.

Intestinal obstruction

A complication that’s often associated with abdominal desmoid tumors is intestinal obstruction, which is a medical emergency. When this occurs, you may experience symptoms like:

Contact a doctor immediately if you’re experiencing these types of symptoms.

Ureter obstruction

Another complication that can happen is ureter obstruction, which is when the tubes leading from your kidneys to your bladder become blocked. This can potentially lead to kidney damage and can cause symptoms such as abdominal pain and possibly decreased urine volume.

Don’t hesitate to contact a doctor if you’re experiencing these symptoms.

Desmoid tumors come from a type of cell called a fibroblast. These cells are components of connective tissue and play a role in healing wounds.

It’s not known what exactly causes these cells to begin to grow and divide out of control. However, genetics appears to play a large role.

About 85 percent of desmoid tumors have a mutation in a gene called CTNNB1. This gene encodes for a protein that’s important for controlling genes that are involved in cell growth.

Desmoid tumors, particularly abdominal desmoid tumors, also happen more often in people with a genetic condition called familial adenomatous polyposis (FAP). FAP is associated with the development of cancers in the colon and rectum.

In addition to having FAP, some other risk factors for abdominal desmoid tumors include:

  • being assigned female at birth
  • younger age, with peak occurrences between ages 30 and 40
  • pregnancy
  • exposure to high levels of estrogen
  • previous abdominal injury or surgery

Some people with abdominal desmoid tumors may not experience symptoms. Because of this, it’s possible that a tumor may be found during screening or testing for other health conditions affecting the abdomen.

If you do have symptoms, your doctor will first request your medical history and perform a physical exam. They’ll ask you about your symptoms, when they first started, and if anything makes them better or worse.

They will then order imaging tests to get a look at the tumor, its size, and where it’s located. Several different types of imaging technology may be used, including:

To confirm that your tumor is a desmoid tumor and not another tumor type, your doctor will also take a biopsy. This is a tissue sample from the tumor that can be analyzed in a lab under a microscope to determine the type of tumor that you have.

If you have an abdominal desmoid tumor and do not have symptoms, your doctor may recommend watchful waiting, during which they’ll continue to monitor your tumor over time. It’s possible for some desmoid tumors to shrink on their own.

Treatment is typically initiated when an abdominal desmoid tumor is causing symptoms or is steadily growing larger.

Surgery

The main approach to treating an abdominal desmoid tumor is surgery. The goal is to remove as much of the tumor as is safely possible. Following surgery, the affected part of the abdominal wall may need to be reconstructed, often using a prosthetic mesh.

Other treatments

If surgery is not an option, abdominal desmoid tumors can also be treated medically. These types of treatments can include:

  • Chemotherapy. Chemotherapy drugs target and destroy quickly growing cells, such as those found in a tumor. Some types of chemotherapy can be effective against desmoid tumors.
  • Targeted therapy. Targeted therapy drugs disrupt specific proteins important for tumor growth. Pazopanib (Votrient) and sorafenib (Nexavar) are two targeted therapy drugs that may benefit people with desmoid tumors.
  • Radiation. This treatment involves using high-energy radiation to destroy tumor cells. Radiation may also be used to remove remaining tumor cells following surgery. This is called adjuvant therapy.
  • Hormone therapy. Because the growth of desmoid tumors appears to be tied to hormones, specifically estrogen, hormone therapy with drugs like tamoxifen may help with desmoid tumors.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs). Some NSAIDs work to inhibit a pathway that’s involved in desmoid tumor growth and may be used to treat desmoid tumors. Examples include sulindac and meloxicam.

The outlook for an abdominal desmoid tumor can vary greatly by individual. Factors that impact outlook include:

  • the size of your tumor
  • how fast it’s growing
  • where in your abdomen it’s located
  • whether it can be removed via surgery

Generally speaking, abdominal desmoid tumors typically respond well when they can be removed through surgery.

For example, a 2014 study looked at 50 individuals who underwent surgery for an abdominal desmoid tumor. It found that 46 out of 50 people (92 percent) remained tumor-free over a median follow-up period of 6 years. However, it’s important to note that recurrence is still possible. This is particularly true when all of a tumor cannot be removed.

Overall, your doctor can give you the best information on your outlook and what to expect from treatment. If you have any questions or concerns, don’t hesitate to discuss them.

Abdominal desmoid tumors are benign tumors that originate from connective tissue. They can sometimes grow into surrounding tissue, which can lead to potentially serious complications.

Be sure to see a doctor right away if you notice an unexplained mass or swelling in your abdominal area, especially if it’s painful.