Desmoid tumors are uncommon, noncancerous growths that develop within the body’s connective tissues, which provide structural support. These tumors are also referred to as aggressive fibromatosis. While they do not spread to distant parts of the body, they can infiltrate and damage nearby tissues and organs. Desmoid tumors can arise in numerous locations throughout the body where connective tissue is present.
Understanding Desmoid Tumors
Desmoid tumors originate from connective tissues, found extensively throughout the body, which support and protect other tissues and organs. They are also known as aggressive fibromatosis, desmoid-type fibromatosis, or deep fibromatosis, reflecting their fibrous, scar-like consistency. They commonly appear in the abdomen, arms, and legs, but can also develop in the chest wall, shoulders, and other regions.
A key characteristic is their local aggressiveness; they do not spread through the bloodstream or lymphatic system. However, they can grow to a significant size and invade surrounding nerves, blood vessels, muscles, tendons, or even obstruct intestines, leading to various symptoms. The specific symptoms depend on the tumor’s location and size, ranging from a noticeable lump, pain, or swelling in the affected area to more severe issues like loss of function in a limb or bowel obstruction. While not generally life-threatening, their infiltrative nature can cause pain, disability, and negatively impact a patient’s quality of life.
How Desmoid Tumors Develop
Desmoid tumor formation involves specific DNA changes within connective tissue cells. These genetic alterations cause affected cells to multiply uncontrollably, leading to tumor development. Most desmoid tumor cases are sporadic, meaning they occur without a clear inherited cause.
In sporadic cases, the tumors are often linked to somatic mutations in the CTNNB1 gene, which are genetic changes acquired during a person’s lifetime and are not inherited. These CTNNB1 mutations account for about 85% of sporadic desmoid tumors. The CTNNB1 gene produces beta-catenin, a protein involved in cell growth and division. A CTNNB1 mutation can lead to an accumulation of abnormal beta-catenin, prompting uncontrolled cell proliferation and tumor formation.
A smaller percentage (5% to 10%) of desmoid tumors are associated with familial adenomatous polyposis (FAP), an inherited genetic condition. FAP is caused by an inherited mutation in the APC gene, which regulates beta-catenin levels. In individuals with FAP, a second somatic mutation in the remaining APC gene copy can trigger desmoid tumor development. Other risk factors include being a young adult (20-30 years old), being female (especially during or after pregnancy), and a history of injury or surgery in the affected area.
Detecting and Managing Desmoid Tumors
Diagnosing a desmoid tumor begins with a physical examination to assess lumps or symptoms. Imaging tests, such as computed tomography (CT) scans and magnetic resonance imaging (MRI), are used to visualize the suspected tumor, its size, and how it relates to surrounding structures. MRI scans are preferred due to their superior soft tissue contrast, making desmoid tumors easier to distinguish from other tissues.
A definitive diagnosis requires a biopsy, where a tissue sample from the tumor is collected and examined by a pathologist. This process confirms the type of cells involved and assesses their aggressiveness, which guides treatment decisions. Core-needle biopsies are the most common method for obtaining tissue samples. Genetic testing of the biopsy can also identify mutations in genes like CTNNB1 or APC, further supporting the diagnosis and informing the patient’s overall care plan.
Treatment approaches for desmoid tumors are varied, depending on factors such as the tumor’s size, location, symptoms, and growth rate. For slow-growing or asymptomatic tumors, active surveillance (“watch and wait”) may be the initial strategy, involving periodic monitoring through imaging tests. If treatment is necessary, surgical removal is an option, although recurrence after surgery is a common concern, especially for tumors in certain locations.
Other modalities include radiation therapy, which uses high-energy beams to target and destroy tumor cells, sometimes used when surgery is not feasible or to reduce recurrence risk. Chemotherapy, using strong drugs to kill tumor cells, may be recommended for rapidly growing tumors or when surgery is not an option. Targeted therapies and hormone therapies, such as anti-estrogen drugs, are also used, with some desmoid tumors showing sensitivity to hormonal manipulation. Cryoablation, a minimally invasive procedure that uses extreme cold to freeze and destroy tumor tissue, is another option for painful or rapidly growing tumors. The unpredictable nature of desmoid tumors, with some regressing spontaneously and others growing quickly, means treatment plans are often individualized and adapted.