Synovial Sarcoma

Synovial sarcoma is a rare soft tissue cancer that grows slowly and often goes unnoticed for years. While it most commonly affects young adults near large joints, it can appear almost anywhere in the body, making early detection challenging but crucial for better outcomes.

Table of contents

• What is synovial sarcoma?
• How common is synovial sarcoma?
• Where does synovial sarcoma form?
• Signs and symptoms
• Causes and genetic changes
• Diagnosis
• Treatment options
• Prognosis and survival
• Living with synovial sarcoma

What is synovial sarcoma?

Synovial sarcoma is a rare type of cancer that affects soft tissues — the parts of your body like muscles, ligaments, and tendons that connect, support, or surround other structures and organs^[1]. The name “synovial sarcoma” comes from the fact that cancer cells under a microscope look similar to cells found in synovial joints (such as your elbows, hips, knees, and shoulders). However, the term is somewhat misleading because this cancer doesn’t actually develop from synovial tissue and can occur almost anywhere in the body^[4].

This cancer is classified as a mesenchymal tumor with partial epithelial characteristics, meaning it shows features of both connective tissue and the tissue that lines organs and surfaces^[4]. One defining feature of synovial sarcoma is a specific genetic change present in more than 90% of cases: a rearrangement between chromosome 18 and chromosome X that creates abnormal fusion proteins^[4].

Synovial sarcoma grows very slowly and may not cause pain initially^[1]. Many people don’t develop symptoms until the tumor grows large enough to create a visible or feelable lump. Because the cancer can grow undetected for up to two years, and because symptoms can resemble other, more common conditions like arthritis or bursitis, diagnosis is sometimes delayed^[1].

How common is synovial sarcoma?

Synovial sarcoma is an uncommon form of cancer. In the United States, approximately 800 to 1,000 new cases are diagnosed each year^[1][4]. According to data from the Surveillance, Epidemiology, and End Results database, the age-adjusted incidence rate is 0.177 per 100,000 people, with a prevalence rate of 0.65 per 100,000^[4].

Anyone can develop synovial sarcoma at any age, but it occurs most commonly in adolescents and adults younger than 30 years old^[1][4]. It is considered the most common sarcoma in the adolescent age group^[4]. The cancer affects males slightly more often than females, with a ratio of approximately 1.2 to 1^[7]. About one third of all patients with synovial sarcoma are diagnosed before age 30^[6].

Where does synovial sarcoma form?

Although the name suggests a connection to joints, synovial sarcoma can develop in various locations throughout the body^[1]. The cancer most commonly appears in the extremities — the arms and legs — often near large joints^[3].

Common sites where synovial sarcoma can form include:

• Arms and legs, particularly near large joints
• Feet and ankles
• Wrists
• Knees
• Shoulders
• Hips
• Elbows

Less commonly, synovial sarcoma can develop in other areas such as the abdomen, lungs, chest, head, or neck^[1][3]. The tumor typically forms in soft tissue of the extremities, including the connective tissue of large joints, but it is not limited to these areas^[3].

Signs and symptoms

Synovial sarcoma develops gradually over time, and tumors can grow undetected for up to two years^[1]. During this time, you may not have any symptoms at all. The most common first sign is an otherwise unexplained swelling or mass^[2][7].

When symptoms do appear, they vary depending on where the tumor is located and its size. Common symptoms include:

• A lump you can see and feel, which may or may not be painful
• Swelling in the affected area
• Pain that lasts a long period of time
• Numbness, especially if the tumor presses on nearby nerves as it grows
• Joint stiffness

When synovial sarcoma occurs in the head or neck, it may cause additional symptoms such as difficulty breathing, problems swallowing, or changes in the voice^[2].

One challenging aspect of synovial sarcoma is that its symptoms can look and feel like symptoms of other, less serious conditions such as arthritis, bursitis, or tendonitis^[1][3]. This similarity can lead to delays in diagnosis or initial misdiagnosis. On average, it can take up to two years from the start of symptoms to diagnosis^[16].

Causes and genetic changes

Researchers are not entirely sure what causes synovial sarcoma to develop. There are no known environmental or inheritable factors associated with this cancer^[4]. However, scientists have identified specific genetic changes that are consistently present in synovial sarcoma cells.

The hallmark feature of synovial sarcoma is a genetic rearrangement involving chromosomes. In more than 90% of cases, there is a translocation — a swap of genetic material — between chromosome 18 and chromosome X^[4][7]. This is written as t(X;18)(p11.2;q11.2) in medical terminology.

During this translocation, a gene called SS18 (also known as SYT) on chromosome 18 joins abnormally with one of several SSX genes on chromosome X^[4][6]. This creates fusion proteins, most commonly SS18:SSX1 or SS18:SSX2, which are expressed in about 95% of synovial sarcoma cases^[4].

To help understand this process, imagine your chromosomes as jigsaw puzzles and your genes as puzzle pieces. Now imagine someone forces a puzzle piece into a spot where it doesn’t belong^[1]. When the SS18 gene jams up against genes that aren’t the right fit, your cells don’t work as they should, and your body develops this mutant gene that leads to synovial sarcoma.

These fusion proteins interact with a complex in cells called the BAF complex, disrupting normal cell function and promoting cancer development^[4]. Researchers do not yet know why this chromosomal rearrangement occurs in the first place^[5].

Diagnosis

Diagnosing synovial sarcoma typically begins with a healthcare provider conducting a physical examination and asking about your symptoms and health history^[1]. If synovial sarcoma is suspected, you will be referred to an oncologist — a doctor who specializes in cancer — for further testing.

Because synovial sarcoma is slow-growing and its symptoms can resemble other conditions, it can take years before a diagnosis is made. Sometimes it is initially misdiagnosed as a joint problem like arthritis or bursitis^[9].

Imaging tests

Various imaging tests are used to see where the tumor is located, determine its size, and check if it has spread to other parts of the body^[1]. These tests might include:

• X-rays
• Magnetic resonance imaging (MRI) — a test that uses magnets and radio waves to create detailed pictures of soft tissues
• Computed tomography (CT) scans — imaging that uses X-rays and computers to create cross-sectional views of the body
• Ultrasound
• Bone scans
• Positron emission tomography (PET) scans — imaging that measures body functions and can show if cancer has spread

Biopsy

A biopsy is essential for confirming the diagnosis. During this procedure, a small tissue sample is removed from the tumor^[1]. The tissue might be removed using a needle inserted through the skin into the tumor, or sometimes surgery is needed to obtain the sample^[2].

The tissue sample is examined under a microscope by a specialist called a pathologist. The pathologist looks at the cells to determine if they are cancerous and, if so, what type of cancer is present^[5].

Special tests

Additional specialized tests are performed on the biopsy sample to provide more details about the cancer cells. The diagnosis of synovial sarcoma is typically made based on how the cells look under a microscope and is confirmed by identifying the characteristic t(X;18) chromosomal translocation^[6][7]. Molecular techniques are used to detect this genetic change, which helps distinguish synovial sarcoma from other types of soft tissue cancers.

Blood tests may also be performed as part of the evaluation process^[5].

Treatment options

Treatment for synovial sarcoma depends on several factors, including the tumor’s size, location, whether it has spread, and the patient’s overall health. The main goal is to remove the cancer completely while preserving as much normal function as possible.

Surgery

Surgery remains the cornerstone and primary treatment for synovial sarcoma^[6][9]. The goal of surgery is to remove the entire tumor along with some surrounding healthy tissue to ensure clear margins — meaning no cancer cells are left at the edges of the removed tissue. This is called wide resection with margins^[5]. A tumor-free margin of 1 to 3 centimeters is typically recommended^[12].

Depending on the tumor’s size and location, surgery can be a significant operation involving cutting into tissue, bone, and muscle, which may leave a long scar^[1]. In the past, surgery for synovial sarcoma in the arms or legs might have included removing the entire limb, known as amputation. However, medical advances have made amputation less common. Today, limb-sparing surgery — procedures that remove the tumor while preserving the limb — is more frequently possible^[9].

When all of the tumor can be removed and there is no sign of cancer elsewhere in the body, there is a better chance of survival^[6]. The success of surgery depends on the tumor’s size and location.

Radiation therapy

Radiation therapy uses powerful energy beams to kill cancer cells. During treatment, you lie on a table while a machine moves around you, directing radiation to precise points on your body^[9].

Radiation may be used before surgery to shrink the tumor, making it easier to remove completely^[1][9]. It can also be used after surgery to kill any remaining cancer cells and lower the chances of the cancer coming back^[5][9]. However, radiation can make healthy tissues less stretchy over time, which might cause some tightness and discomfort^[19].

Chemotherapy

Chemotherapy uses drugs to kill cancer cells throughout the body. The role of chemotherapy in treating synovial sarcoma has been somewhat controversial, but it may be beneficial in certain situations^[4].

Chemotherapy may be used when synovial sarcoma cannot be completely removed by surgery or when it has spread to other parts of the body^[6]. It can be given before surgery (neoadjuvant chemotherapy) to shrink the tumor or after surgery (adjuvant chemotherapy) to reduce the risk of cancer returning^[4]. Some studies have shown that chemotherapy, particularly with drugs like doxorubicin and ifosfamide, can improve survival rates in selected patients, especially those with tumors larger than 5 centimeters^[12].

Chemotherapy is used more regularly in treating children with synovial sarcoma than in adults^[4]. You should discuss the potential benefits and risks of chemotherapy with your doctors.

Emerging treatments

Researchers are investigating new treatment approaches for synovial sarcoma. Recent studies have explored the use of specialized therapies, including targeted treatments and immunotherapies. Some experimental treatments being studied include monoclonal antibodies that target specific proteins on synovial sarcoma cells and vaccines derived from the abnormal fusion proteins characteristic of this cancer^[12].

Prognosis and survival

The prognosis — the expected outcome and course of the disease — varies from person to person. Many factors influence prognosis, including:

• Where the tumor is located in your body
• The size of the tumor
• The depth of the tumor in the body
• Whether the cancer has spread to lymph nodes or other parts of the body
• How much of the tumor could be removed during surgery
• The tumor’s grade — how abnormal the cells look under a microscope

The outlook is generally more favorable if a surgeon can remove the entire tumor before it spreads^[1]. When the tumor is localized — meaning it has not spread — the chances of successful treatment are better. However, synovial sarcoma is an aggressive cancer with a high potential for metastasis, meaning it can spread to other parts of the body^[4]. About half of all cases eventually develop distant spread, often to the lungs, though this may occur months to years after initial diagnosis^[8].

Because synovial sarcoma is so rare, survival rates may not be entirely accurate. Doctors estimate that anywhere from 36% to 76% of people with synovial sarcoma are alive five years after diagnosis^[6]. These statistics represent how groups of people have done in the past and don’t account for newer treatments being developed.

Early diagnosis and treatment are helping people with synovial sarcoma live longer, with hope for a cure^[1]. If you want information about your personal prognosis, it is important to talk with your doctor, as every person’s situation is different.

Living with synovial sarcoma

Living with synovial sarcoma presents physical, practical, emotional, and spiritual challenges. Recovery and adjustment after treatment is different for each person, depending on where the cancer was located, the stage of cancer, what was removed during surgery, the type of treatment received, and many other factors.

Follow-up care

After treatment ends, regular follow-up appointments with your doctors are very important. During these visits, your doctors will ask about any problems you’re experiencing and may perform physical exams, laboratory tests, X-rays, or scans to look for signs of cancer returning or treatment side effects.

At first, follow-up visits may be scheduled every 3 to 6 months. After 2 to 3 years, you may transition to visits every 6 months for a few more years, followed by at least yearly check-ups for a long time after that^[21]. Chest X-rays and other imaging tests of the area where the tumor was located are typically performed at some of these visits to watch for any signs that the cancer has come back.

Rehabilitation and physical recovery

Rehabilitation can be an important part of healing after treatment, especially for synovial sarcoma affecting an arm or leg. Physical therapy with exercises prescribed by your physiotherapists will gradually make moving easier^[19]. You may have trouble moving the affected limb initially, but most people regain significant function within a year of surgery.

Major surgery involving removal of muscle groups can affect how your body moves and works. Some changes may be temporary, while others are long-lasting or permanent^[20].

Emotional and psychological impacts

You may experience a range of emotions during and after treatment, including feeling shocked, upset, numb, frightened, uncertain, confused, angry, or guilty^[19]. All of these feelings are natural parts of coming to terms with cancer. The journey with synovial sarcoma can be frustrating and may involve challenges with diagnosis and treatment, leading to feelings of uncertainty^[16].

Body image and self-esteem may be affected by scars, changes in appearance, or loss of function. How you look is an important part of your self-esteem, and it can be difficult to accept sudden changes you’re not happy with^[19]. Remember that people closest to you will not see you differently as a person. Try to talk with them — they can help support you when they know how you feel.

If you have had an amputation, it can take many months before you’re comfortable with a prosthetic limb and can put weight on it normally. Some people experience phantom limb pain — sensations of pain, burning, throbbing, cramping, or itching in the amputated limb^[20]. This occurs because nerves are cut during surgery, causing the body to send abnormal nerve signals. Phantom limb pain usually begins 1 to 4 weeks after surgery and typically lessens during the first year, though for some it can become a long-term problem.

Support and resources

You don’t have to face these challenges alone. Various sources of support are available:

• Your healthcare team can arrange counseling if you need it
• Support groups can connect you with others who understand what you’re going through
• Organizations like Sarcoma UK provide help and support specifically for people with bone or soft tissue sarcomas^[19]
• Talking with other people who have experience with cancer can provide comfort and practical advice

Taking in information can be difficult, especially when you’ve just been diagnosed or received news about your outlook. It’s okay to ask your doctors and nurses to explain things again if you need them to. You might feel that you don’t want to know much information right away — that’s also okay. You can always ask for more information when you feel ready^[19].

Practical strategies that may help include making lists, keeping a calendar with all appointments, setting goals, and planning enjoyable activities around weeks that might be emotionally difficult^[19]. While it’s not yet clear if specific lifestyle changes can prevent synovial sarcoma from returning, adopting healthy behaviors such as not smoking, eating well, getting regular physical activity, and staying at a healthy weight might help and can have positive effects on your overall health^[22].