Getting a desmoid tumor diagnosis can be confusing, and many people receive incorrect diagnoses along the way. One member of MyDesmoidTumor Team member shared, “I really don’t know what kind of tumors I’m dealing with.” Another member commented, “I have been struggling since 1998 but wasn’t diagnosed until about 2006.”

Desmoid tumors (also known as aggressive fibromatosis) are rare, noncancerous tumors that form in connective tissue. Symptoms of desmoid tumors can vary depending on where the tumor is located, and they can overlap with those of many other diseases, which can lead to misdiagnosis.

If you’re feeling confused or frustrated about the diagnosis process for desmoid tumors, you’re not alone. Receiving a diagnosis can take months or even years, and it’s common for people to be misdiagnosed. Desmoid tumors are often mistaken for lipomas, sarcomas, and other conditions. In this article, we’ll cover some of the conditions that can be confused with desmoid tumors.

How Are Desmoid Tumors Diagnosed?

If you go to your health care provider with symptoms of a desmoid tumor, like pain or a lump, they will consider several possible conditions that could be causing your symptoms and try to find out which one it is. This process is known as identifying a differential diagnosis. Desmoid tumor symptoms are often nonspecific, meaning they can occur in many other conditions. This makes desmoid tumors harder to identify.

To confirm a desmoid tumor diagnosis, doctors typically follow a standard process to rule out other diseases. Depending on where your tumor is located, your doctor may recommend additional tests to check for other conditions. The typical tests for diagnosing a desmoid tumor include:

• A physical examination
• A magnetic resonance imaging (MRI) scan or computed tomography (CT) scan
• A biopsy

A biopsy is the only way to be sure you have a desmoid tumor. During a biopsy, a sample of the tumor tissue is taken and sent to a pathologist for examination and testing. A pathologist is a medical professional trained to identify diseases by studying tissue samples under the microscope. They will determine if the tissue sample is a desmoid tumor or something else. The pathologist may also run tests to check for markers that are specific to desmoid tumors.

Genetic testing can help determine if you have a condition that increases your risk of desmoid tumors. Desmoid tumors are more common in people with familial adenomatous polyposis (FAP). FAP is a rare disease that causes polyps (small tissue growths) in the colon.

What Are Common Misdiagnoses for Desmoid Tumors?

Because desmoid tumors are rare, they are often misdiagnosed as other conditions. Even though desmoid tumors are noncancerous, they are frequently mistaken for cancers or other benign conditions, such as lipomas.

In a 2021 survey of 619 people with desmoid tumors, common misdiagnoses for desmoid tumors included:

• Sarcoma
• Scar
• Muscle injury
• Lymphoma
• Hematoma
• Breast cancer
• Vascular tumor
• Colon cancer
• Other types of cancer

Below, we’ll explore some of the conditions that are commonly mistaken for desmoid tumors.

Lipomas

Lipomas are lumps made of fat tissue. They feel rubbery to the touch. The cause of lipomas is unknown, and they usually don’t cause health problems. Most of the time, they don’t require further treatment. Lipomas can cause symptoms similar to those of desmoid tumors, but they are much more common than desmoid tumors. Lipomas tend to appear in people aged 40 to 60 years, whereas desmoid tumors are more common in younger people.

Although lipomas and desmoid tumors are found in similar tissue types, it can be harder to tell them apart based on exam. However, a biopsy can help your doctor figure out whether you have a lipoma or a desmoid tumor.

Soft Tissue Sarcomas

Soft tissue sarcomas are cancers that can form anywhere in the body. It’s unclear what causes soft tissue sarcomas, but they start in soft tissues such as muscles, fat, and tendons. There are over 50 types. The main symptoms of soft tissue sarcomas are noticeable lumps, swelling, or pain. These are similar to the symptoms of desmoid tumor.

Desmoid tumors are often mistaken for soft tissue sarcomas because they affect the same tissues, have similar symptoms, and look alike on tests used for diagnosis. It’s important to get the right diagnosis, because desmoid tumors and sarcomas require very different treatments. If you’re unsure about your diagnosis, it’s a good idea to look for a second opinion.

Scar Tissue, Muscle Injury, and Hematomas

Desmoid tumors can sometimes be caused by serious injury or repeated injury to the same area. Muscle injuries, scars, and hematomas (bruises or broken blood vessels) can be caused by similar events. They can also impact similar parts of the body as desmoid tumors and have similar symptoms, such as pain, a lump, and swelling. Scar tissue can also look similar to a desmoid tumor on some diagnostic tests.

Injuries can often heal on their own over time. However, a desmoid tumor can continue to grow over a long period of time.

Lymphoma

Lymphoma is a type of cancer that originates in the body’s lymphatic system. The lymphatic system is part of the immune system, which fights germs and other diseases. Lymph nodes, which are part of the lymphatic system, are found throughout the body. These lymph nodes can become swollen when someone has lymphoma, causing lumps that can appear in various parts of the body. However, lymphoma also causes other symptoms like itching and fever, which are not common with desmoid tumors.

Colon Cancer

Colon cancer starts in the large intestine. The intestine is part of our digestive system. Colon cancer usually affects older adults more than younger ones. Like desmoid tumors, colon cancer can cause a lump in your abdomen (the area where your stomach, intestines, and other organs are located). However, those are the only similarities between these conditions.

Colon cancer usually causes fatigue, weakness, weight loss, and changes in bowel movements, such as diarrhea or constipation. Weight loss or fatigue aren’t common in people with desmoid tumors. However, intra-abdominal desmoid tumors can sometimes cause nausea and vomiting.

If genetic testing reveals you have FAP, you may have both colon cancer and a desmoid tumor at the same time. If you have FAP, it’s important to talk to your doctor about your options for managing the disease.

Other Cancers

Desmoid tumors can sometimes be mistaken for other cancers because they grow in similar areas. Although desmoid tumors cause lumps that grow, just like some cancers, these tumors are only locally invasive, which means they only affect the area where they start and do not spread to other parts of the body (metastasize). They are noncancerous and are usually not life-threatening.

Getting a Second Opinion

Organizations like the Desmoid Tumor Research Foundation and desmoid tumor experts encourage people to seek a second opinion about their diagnosis or treatment plan if they have concerns.

There are many reasons you might want to get a second opinion, including:

• You’re not sure if your diagnosis is correct.
• Your doctor or hospital doesn’t have experience treating desmoid tumors.
• Your doctor suggests major surgery and you want another perspective.
• You would feel more comfortable getting additional information from another doctor.

If your current doctor doesn’t have experience treating desmoid tumors, you may want to find a sarcoma specialist. Sarcoma specialists are oncologists who have expertise caring for people with sarcomas and soft tissue tumors like desmoid tumors.

Getting expert care is important for diagnosis and treatment. Studies show that 30 percent to 40 percent of desmoid tumors are misdiagnosed after a biopsy. Having your biopsy reviewed by a pathologist who specializes in soft tissue tumors can help ensure you have a correct diagnosis.

Once you have the correct diagnosis, working with desmoid tumor experts will help you receive the best care possible.

Find Your Team Today

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 questions about your diagnosis? Do you have a diagnosis story to share? How long did it take you to get your diagnosis? Share your experience in the comments below, or start a conversation by posting on your Activities page.