Desmoid tumor

A desmoid tumor is an abnormal growth that arises from connective tissue, which is the tissue that provides strength and flexibility to structures such as bones, ligaments, and muscles. Affected individuals typically develop a single tumor, although some have multiple tumors. Desmoid tumors most often develop when people are in their 30s or 40s, although they can occur anytime between adolescence and late adulthood.

Tumors that form in the abdomen or abdominal wall are called abdominal desmoid tumors, those that arise from the tissue that connects the abdominal organs are called intra-abdominal desmoid tumors, and tumors found in other regions of the body are called extra-abdominal desmoid tumors. Extra-abdominal tumors occur most often in the shoulders, upper arms, and upper legs.

Desmoid tumors are fibrous, much like scar tissue. They are generally noncancerous (benign) because they do not spread to other parts of the body (metastasize); however, they can aggressively invade the surrounding tissue and can be very difficult to remove surgically. Desmoid tumors can recur, even after they are removed. In about 20 percent of cases, the tumors shrink or disappear with minimal or no treatment (spontaneously regress).

Desmoid tumors may not cause any signs or symptoms. When they do cause symptoms, the most common one is pain. The pain is often due to the tumor pressing against nearby organs, tissues, or blood vessels. Other signs and symptoms are often caused by growth of the tumor into the surrounding tissue, and they can vary based on the size and location of the tumor. Intra-abdominal desmoid tumors can block the bowel, causing constipation. Extra-abdominal desmoid tumors can restrict the movement of affected joints, making it difficult to move the arms or legs.

Desmoid tumors can also occur in combination with other conditions. Desmoid tumors are found in 10 to 30 percent of people with an inherited form of colon cancer called familial adenomatous polyposis (FAP). These individuals typically develop intra-abdominal desmoid tumors in addition to abnormal growths (called polyps) and cancerous tumors in the colon. Desmoid tumors that are not part of FAP are described as sporadic.