A desmoid tumor is a specific type of fibrous growth that occurs in the body. These tumors frequently begin in the arms, legs, or torso. Doctors often refer to them as desmoid-type fibromatosis. Another name for a desmoid tumor is deep fibromatosis.
Desmoids are related to a group of cancers called soft tissue sarcoma. But desmoid tumors are not a cancer because they do not spread to other parts of the body. Often they do not grow or cause symptoms, but some desmoids can grow aggressively. When this happens, these tumors can cause pain or swelling.
Some desmoids can be monitored but don’t need other treatment. Others can be aggressive, and are best treated by doctors who specialize in caring for people with soft tissue sarcoma.
Desmoid tumors can begin anywhere in the body. They most commonly grow in the abdomen as well as the arms and legs.
Most desmoid tumors appear to be linked to a genetic mutation in the CTNNB1 gene. Desmoids associated with a CTNNB1 mutation often develop during or after pregnancy. Some are associated with previous injury. Lesions developing during pregnancy occur in the abdominal wall and may go away on their own.
In rare cases, desmoids are linked to a genetic condition called familial adenomatous polyposis (FAP). FAP is commonly associated with colon cancer, but it can also cause desmoid tumors to form in a subset of FAP patients with Gardner’s syndrome. At least 10 percent of people with FAP develop a desmoid tumor.
The most common sign of a desmoid tumor is a hard lump in the arms, legs, or abdomen. In some cases, the lump is painful.
Doctors use imaging to detect desmoid tumors. An MRI or CT scan can show how extensive the tumor is. Desmoids rarely spread to other parts of the body, but they can grow in multiple locations. A biopsy is required to be sure of the diagnosis.
Desmoid tumors are rare, so it is important that you receive a diagnosis from a team of doctors that is highly experienced in the diagnosis and treatment of desmoid tumors. Special techniques that detect the CTNNB1 mutation help doctors tell desmoid tumors apart from other types of sarcoma. This in turn may affect which treatments your doctor recommends.
Treatment for a desmoid tumor varies depending on the size of the tumor and where it is located. While surgery to remove a desmoid has often been prescribed in the past, it does not provide a cure for everyone.
At Memorial Sloan Kettering, our doctors take a thoughtful approach. We balance our recommendations for surgery with the aggressiveness of each person’s individual tumor. Sometimes we may recommend active surveillance, cryoablation, chemotherapy, or other drug therapies to treat the tumor. These approaches can minimize the risk of complications developing from a desmoid.
Desmoid tumors cannot spread to other parts of the body. For that reason, Memorial Sloan Kettering doctors recommend a conservative approach to treating a desmoid that has come back after initial treatment. We make our recommendations based on genetic information about the tumor and the likelihood that it will continue to grow and cause problems. We sometimes recommend radiation therapy or drug therapies for a tumor than cannot be removed surgically.
The risk for recurrence is different for each person. It depends on a variety of factors.
Because of our extensive experience with desmoid tumors, Memorial Sloan Kettering developed a prediction tool to better understand the risk of a tumor coming back at three, five, and seven years after surgery. This type of tool is called a nomogram.
We strongly recommend that people use the nomogram in partnership with a doctor who is experienced in the management of desmoid tumors.