What is a desmoid tumor?
A desmoid tumor is a rare, noncancerous (benign) soft tissue tumor that develops in connective tissue and can form almost anywhere in the body. These tumors are also known as aggressive fibromatosis, desmoid fibromatosis, or desmoid-type fibromatosis.
Although desmoid tumors do not spread (metastasize) to other parts of the body, they can be locally aggressive and may grow into nearby tissues and structures. These tumors can vary in how quickly they grow and may sometimes remain stable or even shrink without treatment.
Even though they are not cancerous, desmoid tumors are treated by sarcoma specialists at Penn Medicine because they can behave like soft tissue tumors in how they grow and affect nearby structures. We work closely with orthopaedic oncology experts to provide coordinated care based on your needs.
Signs and symptoms of desmoid tumors
Many desmoid tumors do not cause symptoms in the early stages. Symptoms often depend on the tumor’s size and location, and some tumors may not cause problems even as they grow.
When symptoms do occur, they may include:
- A noticeable lump
- Pain or soreness
- Swelling
- Tingling if the tumor presses on nerves
- Abdominal pain, bloating, or constipation if the tumor presses on the intestines or causes a blockage
What causes desmoid tumors?
Doctors do not always know what causes desmoid tumors. These tumors are rare and can occur at any age, but they’re most often diagnosed in people between ages 15 and 60 and are more common in adults assigned female at birth. Most tumors occur without a clear reason, but certain factors may increase the risk of developing a tumor.
People with a genetic condition called familial adenomatous polyposis (FAP) have a higher risk of developing desmoid tumors. FAP also causes growths, called polyps, in the colon and rectum. These polyps can become cancerous over time. Desmoid tumors related to FAP are more likely to occur in the abdomen.
Some desmoid tumors develop after an injury or surgery in the same area, although this is not always the case. In the breast, they may also be linked to prior surgery or implants.
Desmoid tumors are more common during or after pregnancy, which may be related to hormonal changes, especially estrogen. Some tumors may grow during pregnancy, and some may shrink after menopause or respond to hormone-based treatments.
Desmoid tumor diagnosis
A physical exam by a health care provider may reveal a lump or swelling, depending on where the tumor is located. During the exam, your provider will ask about your symptoms and medical history. If a desmoid tumor is suspected, imaging tests may be used to look more closely at the area and determine the size and location of the tumor. A biopsy is then used to confirm the diagnosis. If test results or family history suggest FAP, genetic testing may be recommended.
How are desmoid tumors treated?
Some desmoid tumors do not need immediate treatment, especially if they’re not growing or causing symptoms. Some tumors remain stable for long periods, and a small number may shrink on their own. Instead of treatment, doctors may recommend watchful waiting, which means regular monitoring over time.
If a tumor is growing or causing problems, treatment options may include medicines, minimally invasive procedures, surgery, or other therapies used to control tumor growth. At Penn Medicine, your case may be reviewed by a multidisciplinary group of specialists called a tumor board to help create a treatment plan.
Trusted care for desmoid tumors
Desmoid tumors can be complex and require specialized care. Choosing a program with experience diagnosing and treating these rare tumors is important to support the best results and long-term health.
The Penn Medicine Sarcoma Program brings together specialists in surgical oncology, medical oncology, radiology, pathology, and orthopaedic oncology to evaluate each case and develop a treatment plan. Because desmoid tumors can behave differently, care is tailored to how the tumor grows, where it is located, and your individual needs.
Our team has experience treating a high volume of soft tissue tumors, including desmoid tumors. Whether your tumor requires close monitoring or treatment, you'll receive expert care every step of the way.
Rated “exceptional” by The National Cancer Institute
Penn Medicine’s Abramson Cancer Center is a world leader in cancer research, patient care, and education. Our status as a national leader in cancer care is reflected in our continuous designation as a Comprehensive Cancer Center by the National Cancer Institute (NCI) since 1973, one of 7 such centers in the United States. The ACC is also a member of the National Comprehensive Cancer Network, one of a select few cancer centers in the U.S., that are working to promote equitable access to high-quality, advanced cancer care.