Desmoid tumor symptoms differ based on where the tumors occur. Desmoid tumors most often happen in the abdomen, arms and legs. But they can form anywhere in the body.

In general, signs and symptoms include:

• A mass or area of swelling
• Pain
• Loss of function in the affected area
• Cramping and nausea, when desmoid tumors occur in the abdomen

When to see a doctor

Make an appointment with your doctor if you have any persistent signs or symptoms that worry you.

It's not clear what causes desmoid tumors.

Doctors know these tumors form when a connective tissue cell develops changes in its DNA. A cell's DNA contains the instructions that tell a cell what to do. The changes tell the connective tissue cell to multiply rapidly, creating a mass of cells (tumor) that can invade and destroy healthy body tissue.

Factors that may increase the risk of desmoid tumors include:

• Young adult age. Desmoid tumors tend to occur in younger adults in their 20s and 30s. This tumor is rare in children and older people.
• A genetic syndrome that causes many colon polyps. People with familial adenomatous polyposis (FAP) have an increased risk of desmoid tumors. FAP is caused by a gene mutation that can be passed down from parents to children. It causes numerous growths (polyps) in the colon.
• Pregnancy. Rarely, a desmoid tumor may develop during or soon after pregnancy.
• Injury. A small number of desmoid tumors develop in people who've recently had an injury or surgery.

Tests and procedures used to diagnose desmoid tumors include:

• Physical exam. Your doctor will examine your body to better understand your signs and symptoms.
• Imaging tests. Your doctor may recommend imaging tests, such as CT and MRI, to create pictures of the area where your symptoms are occurring. The images may give your doctor clues about your diagnosis.

• Removing a sample of tissue for testing (biopsy). To make a definitive diagnosis, your doctor collects a sample of the tumor tissue and sends it to a lab for testing. For desmoid tumors, the sample can be collected with a needle or with surgery, depending on your particular situation.

  In the lab, doctors trained in analyzing body tissues (pathologists) examine the sample to determine the types of cells involved and whether the cells are likely to be aggressive. This information helps guide your treatment.

Treatments for desmoid tumors include:

• Monitoring the growth of the tumor. If your desmoid tumor causes no signs or symptoms, your doctor may recommend monitoring the tumor to see if it grows. You may undergo imaging tests every few months. Some tumors never grow and may never require treatment. Some tumors may shrink on their own without any treatment.
• Surgery. If your desmoid tumor causes signs and symptoms, your doctor may recommend an operation to remove the entire tumor and a small margin of healthy tissue that surrounds it. But sometimes the tumor grows to involve nearby structures and can't be completely removed. In these cases, surgeons may remove as much of the tumor as possible.
• Radiation therapy. Radiation therapy uses high-powered beams, such as X-rays and protons, to kill tumor cells. Radiation therapy may be recommended instead of surgery if you're not healthy enough for surgery or if the tumor is located in a place that makes surgery risky. Radiation therapy is sometimes used after surgery if there's a risk that the tumor might return.

• Chemotherapy and other medications. Chemotherapy uses strong drugs to kill tumor cells. Your doctor may recommend chemotherapy if your desmoid tumor is growing quickly and surgery isn't an option.

  Several other drug treatments have shown promise in people with desmoid tumors, including anti-inflammatory drugs, hormone therapies and targeted therapies.

With time, you'll find what helps you cope with the uncertainty and distress of being diagnosed with a rare tumor. Until then, you may find that it helps to:

• Learn enough about desmoid tumors to make decisions about your care. Ask your doctor about your condition, including your test results, treatment options and, if you like, your prognosis. As you learn more about desmoid tumors, you may become more confident in making treatment decisions.
• Keep friends and family close. Keeping your close relationships strong will help you deal with your diagnosis. Friends and family can provide the practical support you'll need, such as helping take care of your home if you're in the hospital. And they can serve as emotional support when you feel overwhelmed.
• Find someone to talk with. Find a good listener who is willing to hear you talk about your hopes and fears. This may be a friend or family member. The concern and understanding of a counselor, medical social worker, clergy member or support group also may be helpful.

Make an appointment with your doctor if you have any signs or symptoms that worry you. If your doctor suspects that you might have desmoid tumor, he or she may refer you to a doctor who specializes in treating cancer (oncologist).

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as fasting before having a specific test.

Gather the medical records that pertain to your condition and bring them to your appointment. If you're seeing a new doctor, ask your previous doctor to forward files and other information, such as glass slides that contain tissue samples, to your new doctor.

Make a list of:

• Your symptoms, including any that seem unrelated to the reason for your appointment
• Key personal information, including major stresses, recent life changes and family medical history
• All medications, vitamins or other supplements you take, including the doses
• Questions to ask your doctor

Consider bringing a family member or friend to help you remember the information you're given.

For desmoid tumors, some basic questions to ask your doctor include:

• What's likely causing my symptoms?
• Other than the most likely cause, what are other possible causes for my symptoms?
• What tests do I need?
• What's the best course of action?
• What are the alternatives to the primary approach you're suggesting?
• What will happen if I don't have surgery or other medical treatments for my condition?
• I have other health conditions. How can I best manage them together?
• Are there restrictions I need to follow?
• Should I see a specialist?
• Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you several questions, such as:

• When did your symptoms begin?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• What else should I know about you that will help me make the right recommendations about your care?