Desmoid tumors are noncancerous growths that develop in connective tissue, such as muscle. They can grow almost anywhere in the body.

Although these tumors are benign, they can grow fast and may be difficult to remove.

Desmoid tumors are very rare. In the United States, about 900 people receive a diagnosis of this condition every year.

In this article, we look at the causes and treatment of desmoid tumors, as well as the outlook for people with these growths.

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A desmoid tumor can grow almost anywhere on the body.

A desmoid tumor grows from connective tissue, which binds organs and tissues together throughout the body.

The connective tissue contains cells called fibroblasts that provide structural support and protection to vital organs. Genetic mutations in fibroblasts can cause them to grow uncontrollably. At this stage, they become desmoid tumors.

These tumors do not spread. However, they can grow so large that they interfere with vital bodily functions. For example, they can compress the lungs, liver, intestines, or other vital organs. They can also move into nearby tissues and structures.

Desmoid tumors can be difficult to remove, which means that they may be life threatening.

Depending on its location in the body, a desmoid tumor may not cause any symptoms.

The most common symptom of a desmoid tumor is a relatively firm mass or lump, which often causes mild pain. Other symptoms include:

  • rectal bleeding and severe abdominal pain, when a desmoid tumor in the abdomen places pressure on the intestines
  • localized pain or stiffness, when a desmoid tumor compresses nerves, blood vessels, or an organ
  • limping and other mobility difficulties
  • loss of sleep
  • anxiety

Due to the wide range of possible sites for a desmoid tumor, its symptoms may vary a great deal.

Although desmoid tumors can grow in most parts of the body, they typically develop in the shoulders, legs, or upper arms. They also commonly grow in and around the abdominal organs, such as the intestines.

For this reason, doctors often describe desmoid tumors as being either intra-abdominal or extra-abdominal. Intra-abdominal desmoid tumors grow inside the abdomen, while extra-abdominal desmoid tumors develop outside of it.

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A CT scan can help diagnose a desmoid tumor.

The diagnosis of a desmoid tumor typically begins with an ultrasound of the growth.

The doctor will also use a biopsy to check for cancerous cells and rule out other potential causes of the tumor. To perform the biopsy, they will generally remove either a few cells or the whole tumor. They will then send the sample to a laboratory for analysis under a microscope.

After they have confirmed the diagnosis, the doctor will need to assess whether the tumor is attached to nearby organs. This information will determine whether a surgeon can remove it safely.

The doctor might also request an MRI or CT scan. These imaging tests can provide more information about the location and growth rate of the tumor.

It is best to receive treatment for a desmoid tumor from a medical team that specializes in managing sarcomas. The team should include:

  • medical oncologists
  • surgeons
  • radiation oncologists
  • genetic specialists
  • nurses

In some cases, doctors may simply monitor desmoid tumors, as they can sometimes shrink without intervention. The medical community refers to nondividing cancer cells as being in a quiescent state.

Depending on the characteristics of the tumor, a "wait and watch" period is sometimes the best course of action before a person undergoes more intensive treatment.

Surgery

Surgery is a standard treatment for a desmoid tumor, but it is only an option if a surgeon can remove the tumor without damaging the surrounding organs.

The surgeon will also remove a margin of the tissue surrounding the tumor. Desmoid tumors often invade surrounding structures, including blood vessels and organs. Removing the extra tissue reduces the risk of this occurring.

However, surgery is becoming less common for people with a desmoid tumor because the tumor can regrow at its original site after treatment.

Chemotherapy

In this type of treatment, a medical professional intravenously administers medications that target and kill abnormal cells. For a desmoid tumor, doctors commonly use the following drugs:

  • doxorubicin
  • liposomal doxorubicin
  • dacarbazine
  • methotrexate
  • vinorelbine
  • vinblastine

Radiation therapy

A doctor may target the tumor with concentrated radiation to kill the cells. However, the side effects can be severe, and there is a risk of new cancers developing.

Therefore, a person will only receive radiation therapy for a desmoid tumor in very specific circumstances.

Here, read more on radiation therapy.

Thermal ablation

A few treatment centers use intense heat, cold, or focused ultrasound to destroy certain types of desmoid tumor. However, the long term effects of this emerging treatment are not yet clear.

There have also been anecdotal reports of success from the following treatments:

  • nonsteroidal anti-inflammatory drugs (NSAIDs), such as sulindac
  • anti-hormonal agents, such as tamoxifen
  • tyrosine kinase inhibitors, a new treatment that has shown beneficial effects during desmoid tumor management

However, clinical trials have not yet confirmed the safety and effectiveness of these treatments.

After desmoid tumor treatment, a person may need physical therapy to regain function in the original site of the tumor.

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Research is ongoing into the causes of desmoid tumors..

Researchers do not yet fully understand what causes desmoid tumors, but some risk factors increase their likelihood. These include:

  • Genetics: An inherited condition called familial adenomatous polyposis (FAP), which is due to a genetic mutation, can increase the risk of developing colorectal cancer. It also predisposes people to desmoid tumors.
  • Trauma: Some researchers believe that physical trauma, particularly repeated trauma, might play a role in the formation of desmoid tumors. For example, some people develop a desmoid tumor after surgery or chronic injuries.
  • Pregnancy: Rarely, pregnant women develop desmoid tumors, which may be due to a combination of hormones and physical trauma.

However, the reports of a connection between pregnancy and desmoid tumors are primarily anecdotal. There is no reliable evidence that supports this claim.

As desmoid tumors are rare, it is challenging to construct well-controlled studies with large enough numbers of participants to determine their causes. Research is ongoing.

For now, however, no data suggest that any specific intervention can prevent desmoid tumors.

Desmoid tumors are so rare that the National Cancer Institute do not have access to an accurate survival rate.

Most desmoid tumors are unlikely to affect overall life expectancy, but they can cause pain as they grow. They are also difficult to remove and treat.

As desmoid tumors can damage organs, cause internal bleeding, and inhibit organ function, people may require additional surgeries or treatments for these complications.

Desmoid tumors can recur, and people with a desmoid tumor may develop more in the future.

Q:

Do other types of cancer cause desmoid tumors?

A:

No, desmoid tumors are not cancerous themselves, and they do not originate from other cancers.

These tumors grow from fibroblasts, which make up connective tissue.

J. Keith Fisher, M.D. Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.