Desmoid tumors arise from the fibroblast cells in the connective tissues and connective tissue is found throughout the body – supporting internal organs, covering vital organs, and making up tendons and ligaments. Because of this, desmoid tumors can develop almost anywhere in the body but are most common in the abdomen or in the arms and legs (extra-abdominal desmoids).
Desmoid tumors are benign, meaning they are not cancerous. However, they can be very aggressive and the condition is often referred to as “aggressive fibromatosis”. An aggressive tumor is one that continues to grow and be invasive to surrounding tissues, causing life threatening problems if they compress vital organs or blood vessels. Because of their aggressive characteristics, some treatment centers refer to desmoid tumors as a “malignant disease” but this is just describing their tendency to recur and to grow into other structures, desmoids don’t metastasize (spread to other organs) like true malignant tumors.
Desmoid tumors are very rare, with only 900 new cases diagnosed in the U.S. each year. These tumors occur more frequently in women than men (a 2:1 ratio) and occur more often in people aged 15 – 60.1
Signs and Symptoms of Desmoid Tumors
Desmoid tumors affect the “elastic” tissues of the body so they tend to be very mobile and less likely to form a hard “bump”; therefore a tumor may exist a long time before it is noticed. If they are superficial then they tend to be less painful lumps; those that are deep can be very painful if they are pushing on internal organs, nerves or blood vessels.
Causes of Desmoid Tumor
There is no known cause of desmoid tumor. The Familial Adenomatous Polyposis (FAP) gene is linked to desmoid tumor. Individuals with a mutation in the FAP gene have about a 30% chance of developing desmoid tumors in their lifetime.2
Diagnostic Testing for Desmoid Tumor
If a desmoid tumor is suspected, the treating physician will have a patient undergo an MRI of the area of the tumor. An MRI will show how large the tumor is, if it is compressing vital structures (like nerves or blood vessels), and if it is growing along structures (like a sheet) or as a more regular mass. A biopsy is needed to be able to diagnose a desmoid tumor. The type of biopsy depends on the location of the tumor. A pathologist will study the biopsied tissue under a microscope and apply special testing to it in order to diagnose a desmoid.
Although desmoid tumors are not truly a malignant process, they are very aggressive and can result in destruction of vital organs which can lead to loss of function, or in the most extreme circumstances lead to death. Treatment options are numerous but none can cure this disease.
Therefore, it’s highly recommended that someone with a diagnosis of desmoid tumor be treated and followed in a center with experience in managing this disease.
Surgery is often a first line of treatment if the desmoid is able to be removed without causing severe functional problems or being disfiguring. But, because of the way the desmoid tumor grows into and around other structures, it is often not possible to remove the tumor entirely so it will nearly always return (recur). It is important to discuss this with the treating physician before considering surgical removal.
Desmoid tumors have estrogen receptors so there is a theory that estrogen increases the growth of the tumor. Anti-estrogen medications such as Tamoxifen® have been used in managing the growth of the tumors. Anti-prostaglandins (non-steriodal anti-inflammatory medications or NSAIDS) have also been successful in slowing the growth of the tumor so NSAIDS like ibuprophen are often used for treatment of desmoid tumors. Chemotherapy agents such as doxorubicin, dacarabazine and carboplatin have been used for their ability to stop cell grow. The ‘chemo’ medications are very toxic so the use is limited in favor of those that are less difficult to tolerate.
There are new drugs being studied that are showing some benefit for management of desmoid tumors. These are in a class called kinase inhibitors and the names of the medications are Gleevec® (imatinib) and Nexavar® (sorafenib). Access to these medication can be difficult and may require enrolling in a clinical trial.
Radiation therapy may be considered to shrink the tumor if it can’t be removed surgically. It may also be considered in addition to surgery, especially when the tumor can’t be removed completely during surgery.
The importance of careful monitoring of desmoid tumors can’t be stressed enough.
These tumors recur at a very high rate and can be growing quietly, not becoming symptomatic until they have done some real damage to internal organs or surrounding tissues. Regular follow-up visits to a treating physician are necessary to best manage the disease.
1. Mankin HJ, Hornicek FJ, Springfield DS; Extra-abdominal desmoid tumors: a report of 234 cases. J Surg Oncol. 2010;102(5):380.
2. Nieuwenhuis MH, Casparie M, Mathus-Vliegen LM, et al. A nation-wide study comparing sporadic and familial adenomatous polyposis-related desmoid-type fibromatoses. Int J Cancer 2011; 129:256.