What is Desmoid Tumor?
Desmoid tumors are a type of tissue growth that, while not capable of spreading to other parts of the body, can invade local tissues. These are also known by a few other names like aggressive fibromatosis, deep fibromatosis, and musculoaponeurotic fibromatosis. Despite their inability to spread, they can become deeply embedded in the body and could lead to serious health issues or even death. Treating desmoid tumors is a complex process that needs careful discussion by a diverse team of tumor specialists.
These types of tumors tend to return even after surgical removal, leading the World Health Organization (WHO) to categorize them as intermediate locally aggressive tumors. As defined by WHO, a desmoid tumor is a tissue growth that originates in the deep soft parts of the body, tends to grow into nearby tissues, and has a habit of returning, but can’t spread to other body parts. It’s also possible for multiple tumors to grow in the same body part or limb. In cases where surgery or radiation therapy are not possible or won’t guarantee a cure, systemic treatment (using drugs that travel through the bloodstream) is used. Recently, several new drugs have been approved by the United States Food and Drug Administration (FDA) specifically for treating patients with these types of tumors.
What Causes Desmoid Tumor?
The exact cause of desmoid tumors remains unknown. Most of these tumors occur unexpectedly and about 85% are linked to a mutation in the pathway encoded by the CTNNB1 gene. There are three distinct mutations identified, known as 41A, 45F, and 45. The mutation labeled as 45F is linked to higher chances of the tumor returning.
Research has shown that the five-year probability of the tumor not returning varies based on the mutation. For patients with the 45F mutation, the probability is 23%, for those with the 41A mutation, it’s 57%, and for patients without these mutations, the likelihood is 65%.
Desmoid tumors are more frequently observed in people with a genetic condition called familial adenomatous polyposis (FAP), which is caused by a mutation in the APC gene. Most of these FAP-related tumors occur in the abdomen and are more likely to occur where surgery has taken place previously. If patients with FAP have their colon removed to prevent colon cancer, desmoid tumors can actually be a more significant cause of health issues and death.
Desmoid tumors also occur more often in women during or after pregnancy. Though this is based mostly on individual cases, it is believed that abdominal injuries and high levels of estrogen might be potential causes. Desmoid tumors associated with pregnancy generally have better outcomes.
Risk Factors and Frequency for Desmoid Tumor
Desmoid tumor is quite rare, with only 2 to 4 people in a million getting diagnosed with this condition. This means it makes up a tiny 0.03% of all tumor types. Individuals aged between 30 and 40 years are most likely to have desmoid tumors, and it is more noticed in women than in men. It usually occurs in people who are aged between 15 to 60 years.
- Desmoid tumor is considered to be a rare condition.
- About 2 to 4 people in a million get diagnosed with this condition each year.
- It represents a tiny fraction (0.03%) of all tumor types.
- Those aged between 30 to 40 years are most likely to develop desmoid tumors.
- The tumor is more common in women than in men.
- These tumors usually appear in individuals who are between 15 to 60 years old.
- They can show up in different body locations including the abdomen or areas near it.
- About 5% to 10% of these tumors occur in the context of Familial Adenomatous Polyposis (FAP), a genetic condition.
Signs and Symptoms of Desmoid Tumor
A desmoid tumor exhibits various symptoms and can be associated with certain conditions. Generally, it is a slow-growing tumor and can stop growing and even shrink without treatment. It is commonly found in different parts of the body like the abdominal muscle, head and neck, pelvis, and limbs. Interestingly, this type of tumor is often seen in conjunction with pregnancy or the use of contraceptive pills. It can also shrink after menopause, suggesting that female hormones could influence its behavior. Sometimes, desmoid tumors can be related to breast surgery or implants, and about one in four cases have a history of trauma or surgery at the tumor site. These tumors can reoccur in the same place, causing damage to local tissues, but they can’t spread to other parts of the body.
When multiple desmoid tumors are present, the condition is considered “multifocal,” meaning the tumors occur in several places, but don’t spread from one location to another. People with a condition called FAP (Familial Adenomatous Polyposis) are at a much higher risk of developing desmoid tumors, up to 25% higher than the general population. In fact, about 5% of people with desmoid tumors are diagnosed with FAP. The majority of cases occur in late teens, although it can appear at any age. The physical exam doesn’t usually show significant findings unless the tumor causes pressure symptoms. Desmoid tumors can imitate cancer of the organ they’re located in (a breast desmoid tumor may look like breast cancer, for instance), so a biopsy is needed for an accurate diagnosis.
Testing for Desmoid Tumor
Imaging tests such as CT scans and MRIs are commonly used when diagnosing and monitoring the progress of a disease. These scans can help determine the size of the tumor, which parts of the body are affected, and what type of surgery may be needed. An MRI may be more helpful than a CT scan for understanding how the tumor relates to nearby organs.
On the MRI scan, there are different kinds of images – T1-weighted and T2-weighted. On T1-weighted images, these tumors appear either the same intensity as or less intense than muscle. On T2-weighted images, they are brighter in comparison. When a special dye called gadolinium is used, the tumor shows moderate enhancement with dark bands due to collagen bundles.
A histological evaluation, which examines the tissue under a microscope, is required to confirm the diagnosis. A small piece of the tissue, called a biopsy, is taken and analyzed. Preferably, this is an incisional biopsy, where a small piece of the tumor is removed, but a careful needle biopsy could also be used.
Immunostaining is a technique used to identify certain proteins in the cells and it can help distinguish these types of tumors. Proteins like vimentin, alpha-smooth muscle actin, muscle actin, and desmin are typically looked for in this process.
Most guidelines suggest using next-generation sequencing. This advanced technique can be used to identify targets which could potentially be treated using drugs.
Desmoid tumor is more common in adolescents and young adults. As it is associated with a condition called Familial Adenomatous Polyposis (FAP) syndrome, a thorough evaluation with a colonoscopy and genetic testing is recommended for patients who first present with desmoid tumors.
Treatment Options for Desmoid Tumor
There isn’t a one-size-fits-all way to manage a desmoid tumor. In many cases, especially with patients who aren’t showing symptoms, doctors often suggest a “watch and wait” approach. When symptoms do occur, several options can be explored. While surgical removal was once a common treatment, this strategy is used less often because the tumor often comes back and the surgery can have serious side effects. Instead, treatments have vastly improved over the past 20 years.
Surgical Treatment
Surgery aims to keep functionality of the limb and vital structures intact. The goal in other soft-tissue cancer surgeries is to completely remove all signs of cancer (R0 resection). However, when it comes to desmoid tumors, achieving R0 isn’t a requirement, just a desired outcome. While studies have debated the risks of leaving some tumor tissue behind (R1 or R2 resection), the consensus is that this doesn’t necessarily increase the risk of the tumor coming back. Moreover, avoiding a large-scale, complex surgery just to achieve R0 isn’t recommended. Using other treatments alongside surgery may lead to more conservative treatment of desmoid tumors.
Radiation Therapy
Radiation therapy is mainly used after surgery if some tumor remains or if surgery isn’t possible. It’s normally delivered at a dose no greater than 56 Gy due to potential complications. Studies show that adding radiation therapy can lower the recurrence rate in patients with remaining tumor tissue after surgery. However, giving radiation treatment before surgery is not usually recommended.
Systemic Therapy
Systemic therapy, treatment that affects the whole body, is usually reserved for patients whose tumors are growing rapidly or threatening vital structures.
Chemotherapy
Desmoid tumors typically don’t respond to chemotherapy, but some treatments may be beneficial. Doxorubicin-based treatments have shown the best success rates, including combinations with dacarbazine or anti-inflammatory drugs. The response to chemotherapy is typically slow and may occur months after the chemotherapy has ended. For children, a combination of vinblastine and methotrexate may be beneficial, though this can be too toxic for adults. Adults may receive a substitute for vinblastine, vinorelbine, alongside methotrexate.
Targeted Therapy
Targeted therapy using Imatinib and Sorafenib has been shown to be successful in treating desmoid tumors, even in patients without certain genetic mutations. Nirogacestat, a treatment that is the first of its kind approved by the USFDA, also showed significant benefits in clinical trials, including reducing pain and physical symptoms, although it also caused certain severe side effects.
Hormonal Therapy
In the past, doctors might recommend hormonal therapy in combination with anti-inflammatory drugs to treat desmoid tumors. This treatment strategy, however, is no longer recommended.
What else can Desmoid Tumor be?
When trying to diagnose a desmoid tumor, doctors usually need to rule out the possibility of other conditions that might present with similar characteristics. These could include:
- Breast cancer
- Skin-related signs of Gardner’s syndrome
- Hereditary colon polyps
- Fibrosarcoma, a type of tissue cancer
- Stomach and intestinal tumors, often referred to as gastrointestinal stromal tumors
- Inflammatory myofibroblastic tumor, which is a rare soft tissue tumor
- Retroperitoneal fibrosis, characterized by excess fibrous tissue in the abdomen
- Sclerosing mesenteritis, which is inflammation and fibrosis that affects the small-bowel mesentery
- Solitary fibrous tumor, a rare soft tissue neoplasm
In order to ensure the most accurate diagnosis, doctors need to consider these possibilities and conduct appropriate tests.
What to expect with Desmoid Tumor
Desmoid tumors usually won’t result in death unless they’re linked with FAP syndrome. However, they can cause significant health issues because of the local damage they do. Interesting to note, up to one in five people with desmoid tumors can have them disappear naturally on their own. Therefore, it’s crucial to analyze each patient’s case individually.
Surgeons now avoid removing these tumors because the procedure often results in serious health implications and can also prove pointless, given the high chances of these tumors coming back.
Possible Complications When Diagnosed with Desmoid Tumor
Desmoid tumors often cause complications due to the pressure they put on nearby nerve and blood vessels, or because they invade neighboring organs or bones. The effects produced by desmoid tumors can greatly vary, depending on which part of the body the tumor is located in.
Desmoid tumors that are growing at a slow rate (less than 10% in 3 months as seen through imaging) may not produce any symptoms, so doctors may choose to just monitor them rather than treat them right away. However, those patients who experience symptoms like severe pain, deformity, or an issue with their nervous system or blood vessels due to the tumor, may need to start the treatment early.
Preventing Desmoid Tumor
It’s important for both patients and healthcare professionals to understand that desmoid tumors are quite rare. Diagnosing and treating this type of tumor can be difficult, as there isn’t a one-size-fits-all treatment plan. While the term “tumor” can understandably cause worry, it’s crucial that medical professionals clarify to patients the unique characteristics of desmoid tumors, one key point being the low risk of death linked to these tumors.
Genetic counseling and screening colonoscopy should be discussed, especially for teens and young adults. Last but not least, all patients should be encouraged to consider participating in clinical research trials to further our understanding and treatment of this condition.