Desmoid tumors are often treated by sarcoma specialists, so you may wonder if desmoid tumors are a type of sarcoma. In this article, we’ll discuss what desmoid tumors and sarcomas have in common and what makes them different.

What Are Desmoid Tumors and Sarcomas?

Desmoid tumors grow from connective tissue — soft tissue that keeps organs in place and connects ligaments, muscles, and bones. A sarcoma is a type of cancer in the connective tissue or bone. Sarcomas can spread to healthy tissue, which is what makes them a type of cancer.

Desmoid tumors and sarcomas grow in similar locations and are treated by the same specialists. The main difference is that desmoid tumors don’t spread to distant tissues and aren’t considered to be sarcoma. The World Health Organization (WHO) classifies desmoid tumors as “locally aggressive,” meaning they can grow and invade nearby tissues but don’t spread to other parts of the body. They are considered “intermediate,” falling between benign (noncancerous) and malignant (cancerous) tumors. This means that although they aren’t cancerous, they can still cause significant problems where they grow.

How Are Desmoid Tumors and Sarcomas Similar?

Below, we’ll describe the similarities between desmoid tumors and sarcomas and why desmoid tumors may be treated by sarcoma specialists.

1. Desmoid Tumors and Sarcomas Can Begin in Soft Tissue

Although desmoid tumors can develop anywhere in the body, they arise only in soft tissue and are usually found in the arms, legs, or abdomen — areas also commonly affected by soft tissue sarcomas.

2. Desmoid Tumors and Sarcomas Are Rare

Both desmoid tumors and sarcomas are rare. Desmoid tumors affect about 2 to 4 people per million each year worldwide. In the United States, about 18,000 people are diagnosed with sarcoma annually.

3. Desmoid Tumors Share Some Sarcoma Symptoms

Both desmoid tumors and sarcomas can involve the following symptoms:

• Pain
• Swelling or a lump
• Trouble moving the affected limb
• Nausea or weight loss (for an intra-abdominal desmoid tumor)

4. Desmoid Tumors and Sarcomas Share a Risk Factor

Desmoid tumors are sometimes linked to a genetic condition called familial adenomatous polyposis (FAP). This condition causes colon polyps — precancerous growths in the colon. In people with FAP, desmoid tumors can occur after surgery to remove these polyps.

One type of FAP is Gardner syndrome, which involves colon polyps as well as tumors in other locations of the body. Gardner syndrome is a risk factor for sarcomas.

5. Desmoid Tumors and Sarcomas Have a Similar Path to Diagnosis

Both desmoid tumors and sarcomas are first detected through a physical exam. This will help your doctor understand your symptoms.

If a desmoid tumor or sarcoma is suspected, your doctor may order imaging tests. CT scans and MRI can help detect and evaluate both desmoid tumors and sarcomas.

Sarcomas can also be diagnosed by X-rays and bone scans because they can occur in bone. Sometimes, positron emission tomography (PET) scans are used to diagnose sarcomas.

After imaging scans, a biopsy may be ordered to diagnose a sarcoma or desmoid tumor. A biopsy involves taking a small sample of the tumor tissue — or the entire tumor, in some cases — for further examination and testing in a lab. This can help with diagnosis and provide information for the best course of treatment.

6. Desmoid Tumors and Sarcomas Can Be Treated by Cancer Doctors

Desmoid tumors are treated by sarcoma specialists, a group of oncologists with expertise in treating people with sarcomas. They may also be involved in research and clinical trials. Desmoid tumors and sarcomas share some treatment options, including oral targeted therapies and chemotherapy. Oral targeted therapies are medications taken by mouth that target cancer cells without affecting most healthy cells.

Desmoid tumors may not need to be treated if they’re stable and don’t cause serious symptoms. Your care team may recommend active surveillance, also known as watchful waiting or observation. With this approach, you’ll have periodic appointments to check your tumor.

How Are Desmoid Tumors and Sarcomas Different?

Desmoid tumors are not a type of sarcoma. In this section, we’ll discuss the differences between desmoid tumors and sarcomas.

1. Sarcomas Are Cancerous

Sarcomas are cancerous tumors that spread to surrounding tissues. The main reason desmoid tumors are not sarcoma is because they’re not malignant. Desmoid tumors are a type of noncancerous soft tissue tumor. They don’t spread to other areas of the body, but they can grow and become aggressive, potentially damaging surrounding organs and tissues.

2. Desmoid Tumors and Sarcomas Have Different Risk Factors

While FAP is a risk factor for both sarcomas and desmoid tumors, they have some different risk factors, listed below.

Desmoid tumors and sarcomas affect people of different ages. Desmoid tumors are more common in young adults aged 20 to 30. Soft tissue sarcomas affect children and older adults more often. Bone sarcomas are more common in children, teens, and people over 65.

Risk factors associated with desmoid tumors include:

• Female sex assigned at birth
• Injury, or trauma, such as abdominal surgery
• Pregnancy
• FAP

Risk factors associated with sarcomas include:

• Radiation
• Long-term swelling
• Exposure to viruses
• Exposure to chemicals
• Broken bones

3. Sarcomas Can Occur in Other Parts of the Body

Although desmoid tumors are found only in soft tissues like muscles, blood vessels, tendons, and nerves, sarcomas can also be found in bone. Because sarcomas can also start in the bone, a broken bone is a risk factor for sarcomas, not desmoid tumors.

4. Surgery Is Used More Often for Sarcomas Than Desmoid Tumors

Surgery was once the main treatment for desmoid tumors. However, it’s no longer recommended as a first option because of the high chance that the tumors will return. On the other hand, surgery is often a preferred option for sarcomas.

Sometimes, surgery is still used for desmoid tumors, depending on specific circumstances. The tumor’s size, location, and growth rate, as well as the person’s overall health, are important in deciding if surgery is the right choice. Although surgery can remove the tumor, it comes with risks, like possible damage to nearby tissues and the chance that the tumor could come back. Doctors carefully consider each case to determine the best treatment plan, which might also include medication or radiation therapy.

Talk With Others Who Understand

On MyDesmoidTumorTeam, people share their experiences with desmoid tumors, get advice, and find support from others who understand.

Do you have questions about the differences between desmoid tumors and sarcomas? Let others know in the comments below.