Blog

Not all tumors behave in the same way. Some cancers spread from their original location to distant organs, while other growths can become large or invade nearby tissues without spreading throughout the body.

Desmoid tumors are an example of this unusual behavior. They are rare growths that develop from connective tissue, which helps hold the body's structures together. Although they do not usually spread to distant organs, they can grow into nearby muscles, nerves, blood vessels, or other tissues.

What Are Desmoid Tumors?

Desmoid tumors, also called desmoid-type fibromatosis, are rare growths that develop from connective tissue. They may occur in the abdomen, abdominal wall, shoulders, arms, legs, or other parts of the body.

These tumors are classified as locally aggressive but non-metastasizing. This means they can invade nearby tissues, but they do not typically spread to distant organs like many malignant cancers.

Desmoid tumors can behave differently in different people. Some grow slowly, some remain stable for long periods, and others may shrink without treatment. In certain cases, they can grow enough to cause pain or interfere with the function of nearby organs.

Why Do Desmoid Tumors Grow Without Spreading?

The behavior of desmoid tumors is linked to the type of cells involved and the biological changes that drive their growth.

They Develop From Connective Tissue

Desmoid tumors arise from cells called fibroblasts or related connective-tissue cells. These cells normally help produce collagen and maintain the body's structural framework.

In a desmoid tumor, these cells multiply abnormally and form a mass. The growth may extend into surrounding tissues, making it difficult to separate the tumor from nearby structures.

They Usually Do Not Metastasize

Metastasis occurs when cancer cells spread from their original location to distant parts of the body and establish new tumors.

Desmoid tumors generally do not have this metastatic behavior. Instead, their main problem is local growth. A tumor may affect nearby muscles, organs, or nerves without spreading to the lungs, liver, or other distant organs.

This distinction is important because a tumor can still cause serious complications even when it does not metastasize.

Genetic Changes Can Drive Their Growth

Many desmoid tumors contain changes involving the CTNNB1 gene, which affects a cell-signaling protein called beta-catenin. These changes can interfere with normal growth control and encourage cells to multiply.

Some desmoid tumors are associated with familial adenomatous polyposis, an inherited condition linked to changes in the APC gene. However, many people who develop desmoid tumors do not have this inherited condition.

What Are the Symptoms of Desmoid Tumors?

Symptoms depend mainly on the tumor's location, size, and growth rate. Some people notice a lump, while others experience symptoms caused by pressure on nearby structures.

Common symptoms may include:

A firm lump: A mass may develop under the skin or within muscle tissue.

Pain or tenderness: The tumor may cause discomfort as it grows or presses on nearby nerves.

Restricted movement: Growth near a joint or muscle may make movement difficult.

Abdominal discomfort: Tumors inside the abdomen may cause pain, bloating, or pressure.

Bowel problems: In some cases, an abdominal tumor may interfere with the intestines and cause serious complications.

Nerve-related symptoms: Pressure on nearby nerves may cause tingling, weakness, or other changes.

Some desmoid tumors cause no noticeable symptoms and are discovered during imaging performed for another reason.

Sudden severe abdominal pain, vomiting, or a rapidly worsening inability to pass stool or gas requires urgent medical assessment.

What Increases the Risk of Desmoid Tumors?

The exact reason a desmoid tumor develops is not always clear. Several factors may be associated with an increased risk.

Genetic Changes

Changes in CTNNB1 are common in desmoid tumors. People with familial adenomatous polyposis may develop tumors associated with APC gene changes.

Family History

A family history of familial adenomatous polyposis or related inherited conditions may increase the risk. Genetic counseling may be recommended when doctors suspect an inherited cause.

Hormonal Factors

Some desmoid tumors appear to be influenced by hormonal changes. They can occur during or after pregnancy, although they may also develop in people who have never been pregnant.

Previous Tissue Injury or Surgery

Some tumors develop near areas of previous surgery or tissue injury. However, an injury does not necessarily cause a desmoid tumor, and many cases occur without a clear trigger.

How Are Desmoid Tumors Diagnosed?

Doctors use examinations and imaging tests to identify the growth and understand how it affects nearby tissues.

Physical Examination

The doctor checks the lump, its location, and whether it appears to affect movement or nearby structures. Medical history may also help identify possible inherited risk factors.

Imaging Tests

MRI is often useful for tumors in the muscles and other soft tissues. CT scans may be preferred for certain abdominal tumors. Imaging helps doctors assess the size, position, and relationship of the tumor to surrounding structures.

Biopsy

A biopsy involves taking a tissue sample for laboratory examination. A specialist pathologist examines the cells to confirm the diagnosis and distinguish a desmoid tumor from other soft-tissue growths.

Genetic Assessment

If the medical history or tumor findings suggest familial adenomatous polyposis, doctors may recommend genetic counseling or testing. This can help determine whether additional screening is needed.

What Are the Treatment Options for Desmoid Tumors?

Treatment depends on the tumor's location, symptoms, growth, and effect on nearby organs. Because some tumors remain stable or shrink, immediate surgery is not always necessary.

Active Surveillance

Doctors may recommend regular examinations and imaging to monitor the tumor. If it remains stable and causes no major problems, treatment may be delayed.

Medicines

Certain medicines can slow tumor growth or reduce its size. Options may include targeted treatments and other drug therapies selected by a specialist according to the individual case.

Surgery

Surgery may be considered when a tumor causes significant problems or can be removed safely. However, surgery can be complicated because the tumor may extend into nearby tissues, and the growth can return after removal.

Other Treatments

Radiation therapy or other specialized approaches may be considered in selected cases. The treatment team weighs the possible benefits against the risks to nearby tissues and organs.

FAQs

Are desmoid tumors cancerous?

Desmoid tumors are not considered typical metastatic cancers. However, they can invade nearby tissues and cause serious local complications, so medical monitoring is important.

Can desmoid tumors spread to the lungs or liver?

They do not usually spread to distant organs. Their main risk is growth into nearby tissues and structures.

Can a desmoid tumor disappear on its own?

Some desmoid tumors become smaller or stop growing without treatment. Others continue to grow, which is why doctors may recommend regular monitoring.

Are desmoid tumors life-threatening?

Many can be managed successfully, but tumors near important organs or blood vessels may cause serious complications. The level of risk depends on the tumor's location and behavior.

Do all desmoid tumors require surgery?

No. Active surveillance is often considered when a tumor is not causing major problems. Medicines or other treatments may be used if it grows or causes symptoms.

Conclusion

Desmoid tumors are rare connective-tissue growths that can invade nearby tissues but do not usually spread to distant organs. Genetic changes, including changes involving CTNNB1, help explain how they develop and grow. Their behavior varies, with some remaining stable while others cause pain or affect nearby organs. Doctors use imaging, biopsy, and individual assessment to guide care. Depending on the situation, monitoring may be appropriate, while medicines or other treatments may be needed for growing or troublesome tumors.