Synovial sarcoma

A synovial sarcoma is a rare type of soft tissue sarcoma that develops most frequently in tissues deep within the arms, legs, and feet. Also called synovial cell sarcoma, these malignant (cancerous) tumors got their name from similarities to cells in synovial joints—common joints such as the elbows and hips. Despite this connection, synovial sarcoma does not occur within joints.

Synovial sarcoma is the most common soft tissue cancer diagnosed around the foot and ankle. Less often, synovial sarcoma is found in the head, neck, chest, abdomen (belly), pelvis, and back. In some cases, it develops in organs such as the lungs.

Synovial sarcoma often starts as a small mass that doesn’t change for a period of time or may grow quite slowly. It is common for these sarcomas to be present for over a year or more before being diagnosed. As they grow, some tumors invade muscles, bones, nerves, and blood vessels. Synovial sarcomas can also metastasize, most often to the lungs. They may also spread to the bones, lymph nodes, and organs, including the brain.

Synovial sarcoma can recur (come back) to the same spot or spread (metastasize) to another area of the body. Expert, long-term follow-up care is essential to monitor for sarcoma return.

Synovial sarcomas are rare, with under 500 diagnosed in the U.S. each year. The tumors represent just 5 percent of the soft tissue sarcomas found annually. They tend to occur in teens and younger adults, most often affecting males in their 30s.

The Sarcoma Program at Penn Medicine’s Abramson Cancer Center offers one of the nation’s most experienced synovial sarcoma teams. We are experts at diagnosing this challenging cancer and offer sophisticated treatments. Our surgeons can often save arms and legs affected by synovial sarcoma.

Synovial sarcomas are categorized into two types, based on the appearance of the cells in the tumors:

• Monophasic: These tumors are made of just one type of tumor cell, either spindle cells or epithelial cells (less common).
• Biphasic: These tumors include both spindle cells and epithelial cells.

Synovial sarcomas often don’t cause symptoms when they are small. As they grow, you may experience:

• Noticeable lump
• Pain
• Swelling

Cells in almost all synovial sarcomas have genetic changes (translocations). Researchers don’t know for sure why these changes happen.

We do not know definitive factors that may increase your risk for developing one of these tumors.

The most accurate diagnosis of a synovial sarcoma comes from a team like ours that has the experience to know what to look for. At our program, evaluation starts with a physical exam and an in-depth discussion of your symptoms. An imaging scan—usually magnetic resonance imaging (MRI)—can then provide more information about the tumor, including how large it is and its precise location related to other structures. You may have additional scans to see if the sarcoma has metastasized (spread).

To confirm a diagnosis, we will perform an image-guided needle biopsy. A pathologist with expertise diagnosing sarcomas looks at the sample under a microscope and conducts lab tests on it. The molecular “signature” of this sarcoma means that we can be sure of the diagnosis after running the correct tests.

The information from your exam, imaging tests, and biopsy helps our team stage the cancer and plan the most appropriate treatment for you.

Synovial sarcoma treatment almost always involves removing the tumor. As with all sarcoma surgery, the best results come from removing synovial sarcomas in one piece—an approach we are experienced with. Our surgeons also typically remove a border of healthy tissue, to ensure that no cancer cells are left behind.

Adding radiation therapy before the operation reduces the chance that synovial sarcoma returns in the same spot. Chemotherapy may be recommended for larger tumors or ones that have spread (metastasized).

Treatment effectiveness depends on certain tumor characteristics such as:

• Grade: Higher-grade tumors—those whose cells look more aggressive under a microscope—have a higher risk of spreading.
• Size: Tumors that are smaller offer a better prognosis.
• Location: Deeper tumors are more challenging to remove than superficial tumors (closer to the skin).

Our team may recommend chemotherapy for synovial sarcomas that return after treatment or spread. We can also treat with the kinase inhibitor pazopanib, an approved type of targeted therapy designed to stop or slow the growth of cancer cells.

People with advanced disease may also benefit from a sarcoma clinical trial.