Synovial sarcomas
Synovial sarcomas are a rare and aggressive form of soft tissue sarcoma that originate from the tissues associated with joints, most commonly occurring near the knee, ankle, and foot. These tumors can be classified as monophasic or biphasic based on their cellular composition, which can include a mix of epithelial and spindle cells. The incidence of synovial sarcomas is about 8 to 10 percent of all soft-tissue sarcomas, with approximately 800 to 1,000 new cases diagnosed annually in the United States. They predominantly affect individuals between the ages of 29 and 49, and are about 1.2 times more common in men than women.
Symptoms often begin with a non-painful swelling, which may delay diagnosis. Definitive diagnosis typically requires a biopsy, as no specific screening tests exist. The primary treatment is surgical removal of the tumor, often supplemented with radiation therapy. Although chemotherapy's effectiveness remains debated, recent studies on immunotherapies show promise in improving treatment outcomes. The prognosis for synovial sarcoma varies, with better outcomes associated with early detection and certain tumor characteristics, but recurrence is common and the five-year survival rate ranges from 36 to 76 percent.
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Subject Terms
Synovial sarcomas
RELATED CONDITIONS: Soft-tissue sarcomas
DEFINITION: Soft-tissue sarcomas are cancers that begin in fat, cartilage, blood vessels, and muscles. A synovial is a distinct type of soft-tissue tumor that arises from tissues associated with a joint. Most synovial sarcomas are found near joints, though other locations may occur. The tumor can be composed of all epithelial cells, all spindle cells, or a mix of the two cell types. These cells form distinct pink, fleshy masses.
Risk factors: Synovial sarcomas appear to develop because of a genetic mutation. About 90 percent of these tumors show a specific genetic defect that is different from that found in all other sarcomas. This defect involves a switch in a small amount of material on chromosome 18 and the X chromosome. As a result, an incorrect protein is formed.
Etiology and the disease process: Exactly why the genetic mutation occurs or how the resulting protein causes cells to become cancerous is still being studied. Synovial sarcomas are rare and aggressive. The knee joint is the most common tumor location, followed by the ankle and the foot. Primary synovial sarcomas can also develop in the arm, wrist, and hand joints and, less frequently, in the joints of the trunk, head, and neck. Only rarely are primary tumors found in the lungs or abdomen. Synovial sarcomas tend to grow slowly. Often these tumors exist for a long time as hard nodules and then begin to grow suddenly. Sometimes calcium deposits develop in the tumors. Tumors with calcium tend to grow more slowly than those without calcium. Tumors may invade nearby tissues, and between 40 and 70 percent metastasize to distant sites, especially the lungs. This makes synovial sarcoma a highly malignant form of cancer.
Incidence: Synovial sarcomas account for 8 to 10 percent of all soft-tissue sarcomas and are the third most common type of soft-tissue sarcoma. In absolute terms, however, they are quite rare, with only about 800 to 1,000 new cases of synovial sarcoma diagnosed each year in the United States.
Synovial sarcomas are about 1.2 times more common in men than women. They can develop in people of any age, but usually occurs in people between twenty-nine and forty-nine, with the highest incident in those between forty-five and forty-nine.
Symptoms: Most often, the first symptom a person with a synovial sarcoma notices is a swelling that may or may not be painful. Since synovial sarcomas grow slowly, the person may have a hard mass for quite a while, especially if it is not painful, before consulting a doctor. Other symptoms are specific to the location of the tumor. For example, a tumor near a joint may cause pain similar to bursitis or arthritis, or a tumor pressing on a nerve may cause the person to feel numbness and tingling in the surrounding area.
Screening and diagnosis: There are no screening tests specific to synovial sarcoma; however, people who have unexplained swellings or lumps anywhere in the body should consult a physician immediately. Often, diagnosis is delayed because these swellings seem nonthreatening and are not painful, so that by the time they are diagnosed, they have already spread to the or beyond.
Exploration of the tumor begins with a magnetic resonance imaging (MRI) scan. However, a definitive diagnosis can be made only by a biopsy (tissue sample) of the tumor. Depending on the location of the tumor, the biopsy process may be complex (for example, a tumor of the hand). The biopsied tissue is examined under the microscope, where a distinctive pattern of cells identifies it as a synovial sarcoma. The tissue also may be tested for the specific chromosomal abnormalities associated with this cancer.
Staging is done using MRI and computed tomography (CT) scans to determine if the sarcoma has metastasized to distant sites.
Treatment and therapy: The treatment of choice is always surgery, regardless of the stage of the tumor. These tumors tend to spread along the tissues surrounding joints, and it may be necessary to amputate the entire limb to remove all traces of the sarcoma cells. Surgery is supplemented by radiation therapy before and after tumor removal. The use of chemotherapy in addition to surgery and radiation therapy is controversial, with some studies reporting improved survival rates and others reporting no differences in survival when compared with radiation therapy alone. Clinical trials of biological therapies that use synthetic antibodies to target sarcoma cells show promise. Different forms of immunotherapy, including T cell and TBI-1301, as well as adoptive cell therapy were also effective in treating synovial sarcoma and preventing its return.
Prognosis, prevention, and outcomes: There is no known way to prevent synovial sarcoma. Outcomes are better with early diagnosis, when tumors are less than 2 inches (5 centimeters) in diameter, when tumors contain calcium deposits, and when they are located farthest away from the trunk. Recurrence is common, and amputation of a limb is sometimes necessary. The five-year survival rate is between 36 and 76 percent.
Bibliography
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