Synovial sarcoma is a rare type of cancer that tends to occur near large joints, mainly the knees. Synovial sarcoma usually affects young adults.

Synovial sarcoma begins as a growth of cells that can multiply quickly and destroy healthy tissue. The first symptom is usually swelling or a lump under the skin. The lump may or may not hurt.

Synovial sarcoma can occur almost anywhere in the body. The most common places are in the legs and arms.

Synovial sarcoma is a type of cancer called a soft tissue sarcoma. Soft tissue sarcoma happens in the body's connective tissues. There are many types of soft tissue sarcoma.

Symptoms

Signs and symptoms of synovial sarcoma depend on where the cancer starts. Most people notice a painless lump or bump that slowly gets bigger. The lump usually starts near the knee or ankle, but it can appear on any part of the body.

Synovial sarcoma symptoms may include:

• A lump or bump under the skin that slowly gets bigger.
• Joint stiffness.
• Pain.
• Swelling.

Synovial sarcoma that happens in the head or neck can cause other symptoms. These may include:

• Problems breathing.
• Difficulty swallowing.
• Changes in the way the voice sounds.

When to see a doctor

Make an appointment with a doctor or other healthcare professional if you have any symptoms that don't go away and that worry you.

Causes

It's not clear what causes synovial sarcoma.

This kind of cancer forms when cells develop changes in their DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, the DNA gives instructions to grow and multiply at a set rate. The instructions tell the cells to die at a set time. In cancer cells, the DNA changes give different instructions. The changes tell the cancer cells to make many more cells quickly. Cancer cells can keep living when healthy cells would die. This causes too many cells.

The cancer cells might form a mass called a tumor. The tumor can grow to invade and destroy healthy body tissue. In time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer.

Risk factors

Younger age is a risk factor for synovial sarcoma. This cancer happens most often in older children and young adults.

There is no way to prevent synovial sarcoma.

Diagnosis

Synovial sarcoma is usually slow growing, so it can be years before a diagnosis is made. Sometimes, synovial sarcoma is diagnosed in error as a joint problem, such as arthritis or bursitis.

Tests and procedures used to diagnose synovial sarcoma include:

• Imaging tests. Imaging tests take pictures of the body. They can show where a synovial sarcoma is, how large it is and if it has spread to other areas of the body. Tests for synovial sarcoma might include MRI scans, X-rays and CT scans.

• Biopsy. A biopsy is a procedure to remove a sample of tissue for testing in a lab. The tissue might be removed using a needle that is put through the skin and into the cancer. Sometimes surgery is needed to get the tissue sample.

  The sample is tested in a lab to see if it is cancer. Other special tests give more details about the cancer cells. Your healthcare team uses this information to make a treatment plan.

Treatment

Treatment options for synovial sarcoma include:

• Surgery. Surgery is the main treatment for synovial sarcoma. The goal is to remove the cancer and some of the healthy tissue around it. This can sometimes mean the removal of an entire muscle or muscle group.

  In the past, surgery might have included removing an arm or leg, known as amputation. But medical advances have made amputation less likely.

  To lower the chances of the cancer returning, radiation therapy or chemotherapy might be used as well.

• Radiation therapy. Radiation therapy treats cancer with powerful energy beams. During radiation therapy, you lie on a table while a machine moves around you. The machine directs radiation to precise points on the body.

  Radiation before surgery can shrink the cancer and make a successful surgery more likely. Radiation therapy after surgery can kill cancer cells that might still be there.

• Chemotherapy. Chemotherapy treats cancer with strong medicines. For synovial sarcoma, chemotherapy might be used before or after surgery. It also may be used when cancer has spread to other parts of the body.
• Targeted therapy. Targeted therapy uses medicines that attack specific chemicals in the cancer cells. This can cause cancer cells to die or stop growing. Targeted therapy medicines are being studied for advanced synovial sarcoma.
• Cell therapy. Cell therapy helps the immune system find and stop the cancer cells. This treatment involves taking some of your immune system cells and making them better at recognizing the cancer cells. Then the cells are put back in your body. This treatment can take months to set up. One cell therapy used for synovial sarcoma is afamitresgene autoleucel (Tecelra). It might be an option for treating advanced synovial sarcoma that hasn't been helped by chemotherapy.
• Clinical trials. Clinical trials are studies of new treatments. These studies provide a chance to try the latest treatment options. The side effects may not be known. Ask your healthcare team if there is a clinical trial available to take part in.

Preparing for an appointment

Make an appointment with your usual doctor or other healthcare professional if you have any symptoms that worry you. If your health professional thinks you might have synovial sarcoma, you will likely be referred to a specialist.

Specialists who care for people with synovial sarcoma include:

• Doctors who specialize in cancer, called medical oncologists.
• Surgeons who specialize in operating on people with cancers that affect the soft tissue and bones. These surgeons are called orthopedic oncologists.
• Doctors who treat cancer with radiation therapy, called radiation oncologists.

Here is some information that may help you get ready for your appointment.

What you can do

• Write down any symptoms you have. This may include when you first noticed a lump.
• Write down any key medical information. Include any medical conditions or surgeries that you have had.
• Make a list of all medicines, vitamins, or supplements that you're taking. Write down how much medicine you take, when you take it, and the reason you take it.
• Consider bringing a family member or friend. This person can help you remember key information your healthcare professional talks about.
• Write down questions you would like to ask.

Write your questions in order of most important to least important. For synovial sarcoma, some potential questions may include:

• Do I have cancer?
• Do I need more tests?
• What are my treatment options?
• What are the potential risks of these treatment options?
• Do any of the treatments cure my cancer?
• Will I get a copy of my pathology report?
• How much time can I take to consider my treatment options?
• Are there brochures or other printed materials that I can take with me? What websites do you recommend?
• What happens if I choose not to have treatment?

What to expect from your doctor

Your healthcare professional will likely ask you questions that may include:

• What symptoms worry you?
• When did you first notice your symptoms?
• Does anything make your symptoms worse or better?
• How bad are your symptoms?