Diagnosing desmoid tumors can be tricky, so doctors need highly detailed pictures to help. Magnetic resonance imaging (MRI) is an imaging technique capable of scanning nearly every organ, bone, and muscle in the human body. MRI scans are best for diagnosing desmoid tumors outside the abdomen (belly) and monitoring tumor growth over time.

In this article, we’ll cover how MRI scans work and why they’re used to diagnose desmoid tumors. We’ll also discuss other tests doctors use to confirm a desmoid tumor diagnosis.

What Is MRI?

MRI is an imaging technique that creates extremely detailed pictures of nearly every structure in your body. During an MRI, you lie still on a bed that moves through a large, tube-shaped machine. The MRI machine uses powerful magnets to create a strong magnetic field around you. This aligns your body’s atoms in the same direction.

The machine then sends out radio waves that move your atoms out of their original position. As the radio waves turn off, sensors track how your atoms move back into place. A special computer reads the signals created in this process, turning them into detailed pictures.

Some imaging tests — like computed tomography (CT) scans — use X-rays to take pictures. CT scans create radiation that can damage your healthy cells when exposed to high doses. MRI doesn’t use radiation, so it’s safer for certain people.

MRI scans are also better at helping doctors tell the difference between healthy and abnormal soft tissues. Researchers have found MRI is best for finding exactly where a desmoid tumor begins and ends. It also helps doctors see how far a tumor has grown into (infiltrated) a soft tissue like muscle or an organ.

What Happens During an MRI?

If you’ve never had an MRI before, you might not be familiar with the preparation and scanning process. After you arrive at your MRI appointment, you’ll remove anything with metal from your body. This includes glasses, hearing aids, jewelry, and hairpins. The magnet in the MRI machine is extremely powerful and will attract these objects.

You’ll then change into a hospital gown, and a health care provider will start an intravenous (IV) line in your arm or hand. The IV delivers a special liquid called a contrast agent. Some procedures use an oral contrast agent that you drink before your scan. This liquid helps your organs and muscles stand out more in the MRI pictures.

Once you’re ready, you’ll lie on a scan table that moves you through the MRI machine. You’ll lie still throughout the scan to get high-quality pictures. The MRI machine is very loud, so you’ll be given headphones or earplugs to wear. The technician taking your scan may ask you to hold your breath at certain times during the scan to take clear images of your chest and abdomen.

How Do Doctors Use MRI To Diagnose Desmoid Tumors?

When diagnosing desmoid tumors, doctors usually start by using imaging tests to find the tumors. According to the Desmoid Tumor Research Foundation, MRI is preferred for diagnosing desmoid tumors in most cases. This is because MRI has better soft tissue contrast compared to CT scans. Imaging specialists (radiologists) can see soft tissue tumors on MRI scans against muscles and other tissues in the background.

MRI scans are also better at figuring out your desmoid tumor’s degree of cellularity. This refers to the amount of active tumor cells inside your tumor. The MRI machine measures a T2 signal, which reflects how much water is inside a tissue. Desmoid tumors with active cells tend to have more fluid and a higher T2 signal.

Are MRI Scans Enough To Diagnose Desmoid Tumors?

MRI scans are great for finding soft tissue masses in the body. However, they can’t completely confirm that you have a desmoid tumor. Using your MRI scan results, your doctor can perform a biopsy on any potential tumors they find. This test uses a long, thin needle to take a small sample of tumor cells.

A tissue specialist (pathologist) looks at the cells under a microscope to figure out if you have a desmoid tumor. Because desmoid tumors are rare, sometimes they can be misdiagnosed. You may want to get a second opinion from a soft tissue pathologist, a special type of pathologist. It’s important to note that a biopsy is the only way to confirm a desmoid tumor diagnosis.

How Are MRI Scans Used To Monitor Desmoid Tumors?

Desmoid tumors usually grow slowly, so it’s important to track them over time. If you aren’t experiencing any symptoms or you have mild ones, your doctor will monitor your tumor. This is called active surveillance.

Desmoid tumors that aren’t actively growing have more collagen than an early stage, fast-growing tumor. Collagen is a protein with low water content and a low T2 signal on an MRI scan. Your doctor will check your tumor’s cellularity to see if it’s growing or shrinking. Your doctor can also use MRI scans to see if your desmoid tumor treatment is working.

After you’re diagnosed with a desmoid tumor, you’ll likely have an MRI scan within the first month or two. You’ll follow up with scans every three to six months to make sure your tumor isn’t growing larger or spreading. If your desmoid tumor starts progressing, your doctor may make changes to your treatment plan.

What Other Imaging Tests Help Diagnose Desmoid Tumors?

While MRI scans are generally the preferred imaging test, other scans can help diagnose desmoid tumors. The best test depends on where your tumor is located. Extra-abdominal desmoid tumors grow outside your abdomen (belly) and abdominal wall. Common locations include the chest wall, arms, shoulders, and legs. Intra-abdominal desmoid tumors grow along the tissue that covers your intestines.

Research shows that MRI scans work best for diagnosing extra-abdominal tumors. On the other hand, CT scans are better for intra-abdominal tumors.

Pregnancy seems to raise the risk of desmoid tumors. If you’re pregnant and you notice symptoms of a tumor, you’ll likely get an ultrasound to help diagnose a desmoid tumor. This test uses sound waves that bounce off of tissues to create images. Ultrasound is also useful for taking pictures of tumors in the arms, legs, and abdominal wall.

Why Is It Important To Work With a Desmoid Tumor Specialist?

Desmoid tumors are rare and often difficult to diagnose. Imaging tests and biopsy results can look like many other types of soft tissue tumors (sarcomas). Studies show that up to 40 percent of desmoid tumor cases are misdiagnosed, even with a tissue sample.

The Desmoid Tumor Research Foundation recommends working with health care providers who specialize in diagnosing and treating soft tissue tumors. Don’t be afraid to get a second opinion on your test results. A sarcoma specialist will be best prepared to diagnose and treat your tumor. They’re usually associated with academic medical centers or specialized sarcoma treatment centers.

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.

Have you had a magnetic resonance imaging scan to diagnose your desmoid tumor? Have you had active surveillance as well? Share your experience in the comments below, or start a conversation by posting on your Activities page.