Desmoid tumors are noncancerous tumors that grow in the body’s soft tissues. “Intra” means “within,” so intra-abdominal desmoid tumors are tumors that develop within the abdomen. Intra-abdominal desmoid tumors usually occur in the mesentery, “the tissue that holds your organs into place,” explained Dr. Seth Pollack, a sarcoma specialist in Chicago.

Dr. Pollack is the director of the Sarcoma Program at the Lurie Cancer Center and the Steven T. Rosen Professor of Cancer Biology at the Feinberg School of Medicine at Northwestern University.

“There’s a lot of blood vessels that flow through the mesentery that give blood supply to all of your bowels,” Dr. Pollack told MyDesmoidTumorTeam. Desmoid tumors in the mesentery, he said, “can be dangerous because the desmoid tumors can grow into the blood supply that’s really important for your bowels. Desmoid tumors can be invasive, so they could cause bowel obstructions. They could twist a bowel so that things don’t move smoothly through it.”

Risk Factors for Intra-Abdominal Desmoid Tumors

Desmoid tumors are very rare. Having a risk factor associated with a desmoid tumor is not a guarantee that you’ll develop one. The majority of people with the risk factors below do not develop desmoid tumors.

Below are some risk factors associated with desmoid tumors:

• Trauma, such as abdominal surgery, is a risk factor for intra-abdominal and abdominal wall desmoid tumors.
• Pregnancy is a risk factor for desmoid tumors, particularly abdominal wall desmoid tumors.
• Familial adenomatous polyposis (FAP) is a genetic disorder associated with colon cancer. Having FAP increases you risk for developing a desmoid tumor after abdominal surgery, though not everyone with FAP develops one.

Symptoms of Intra-Abdominal Desmoid Tumors

Intra-abdominal desmoid tumors can start as a stomachache and cause very severe pain, Dr. Pollack said. This is different from abdominal wall desmoid tumors, which do not affect the structures inside the stomach.

Abdominal wall tumors can also cause pain in the superficial tissues of the stomach area — that is, the layers of tissue just beneath the skin of the abdomen. People with abdominal wall tumors may also notice a mass or a firmness in the abdomen, he noted.

Dr. Pollack explained that people with intra-abdominal desmoid tumors sometimes go to the emergency room because they’re in such terrible pain.

Diagnosing Intra-Abdominal Desmoid Tumors

Imaging tests are used to diagnose desmoid tumors. For intra-abdominal tumors, computed tomography (CT) scans are the preferred option. Imaging tests can show if you have a mass inside your body. A biopsy of the mass — removal of a piece of tissue to examine under a microscope — is needed to diagnose the condition.

Getting a desmoid tumor diagnosis can be challenging. In some cases, people don’t recognize early symptoms and therefore doesn’t seek help. Getting a diagnosis can also be challenging because desmoid tumors are so rare. In general, rare diseases are commonly misdiagnosed.

People with desmoid tumors might be misdiagnosed as having sarcomas or other cancers. Dr. Pollack noted that when someone with a desmoid tumor arrives at the emergency room with severe stomach pain, they may undergo a scan, which might show a large mass. The doctor might mistake it for a large cancerous tumor. “That will be very scary,” he explained.

Treating Intra-Abdominal Desmoid Tumors

It’s important to get care from specialists with desmoid tumor expertise. These providers may be called sarcoma specialists — oncologists who focus on treating sarcomas. Sarcomas are cancerous tumors that can grow in the bones or soft tissues. Soft tissue sarcomas and desmoid tumors are both types of soft tissue tumors.

When discussing treatment options with your desmoid tumor specialist, talk about your treatment goals and ask what you can expect from each potential approach.

Following are some approaches your care team may consider.

Active Surveillance

Depending on the individual’s circumstances, Dr. Pollack may recommend observing the tumor rather than starting treatment right away. This approach may be called “active surveillance” or “watchful waiting.” If your desmoid tumor care team recommends this approach, you’ll have periodic scans to check your tumor.

Medical Therapy

“I do try and watch these patients when I can,” Dr. Pollack explained — but added, “I’m a bit more aggressive with medical therapy for those mesenteric desmoid patients just because I don’t want those tumors to grow.”

Medical therapy can include chemotherapy or targeted therapies that are taken as a pill. Targeted therapies might include tyrosine kinase inhibitors (TKIs), such as sorafenib (Nexavar), or another type of targeted therapy called nirogacestat (Ogsiveo).

People with intra-abdominal desmoid tumors often find it harder to discontinue medical therapy compared to those with other types of desmoid tumors. “It’s always my goal that we’ll get them off therapy,” Dr. Pollack said. “It’s a little bit easier if the tumors shrank a lot while they’re on treatment.”

Dr. Pollack explained that he tends to treat people with targeted therapies more often than chemotherapy. However, he noted that chemotherapy may be a good option for people who have difficulty with oral medications.

Hormone treatments like tamoxifen and nonsteroidal anti-inflammatory drugs (NSAIDs) are no longer recommended by many desmoid tumor specialists for shrinking tumors, as other very effective options are available. NSAIDs may still be used for pain.

Surgery

“Historically, people were very aggressive surgically with desmoid tumors,” Dr. Pollack explained. Today, surgery is not usually recommended as a first treatment for desmoid tumors because of the high chance the tumor will recur (return).

Surgery may be an option for intra-abdominal wall desmoid tumors that have progressed, depending on the circumstances. The decision to undergo surgery should be considered by a multidisciplinary tumor board (group of medical experts from different specialties).

“My feeling and our feeling at Northwestern is that we still try to avoid surgery because they have a high recurrence rate,” said Dr. Pollack. Additionally, he noted that intra-abdominal desmoid tumors can be hard to remove.

Talk With Others Who Understand

MyDesmoidTumorTeam is the social network for people with desmoid tumors and their loved ones. On MyDesmoidTumorTeam, members come together to ask questions, give advice, and share their stories with others who understand life with desmoid tumors.

Do you have an intra-abdominal wall desmoid tumor? Share your experiences and tips in the comments below, or start a conversation by posting on your Activities page.