A synovial sarcoma is a rare form of cancer that affects the soft tissues of the body.
It typically affects the tissue surrounding the joints in the hands, feet, arms, and legs. It can, however, occur in any soft tissue, as well as the head, neck, and trunk.
Most commonly, synovial sarcoma is found in the tissue, surrounding the joints of the extremities and legs. But it is possible to develop this cancer in soft tissue, including tendons, ligaments, fat, skin, membranes, muscle, and other non-hard tissue anywhere in the body.
Synovial sarcoma is one of the rarest cancers, affecting between 1 and 3 people per million. Although it can occur in any age group or gender, it is most prevalent among teenagers and young adults and affects males more than females.
Doctors divide synovial sarcoma into two main types:
- Monophasic is made up only of spindle cells. Spindle cells are a type of long, slender cell associated with some cancers.
- Biphasic is made up of both normal skin (epithelial) cells and spindle cells.
A third, less common type is called poorly differentiated synovial sarcoma.
In about half of cases of synovial sarcomas, the cancer spreads to other areas of the body. This process is called metastasis, and it increases the risk of a person dying from synovial sarcoma.
Although the cancer can spread anywhere, the lungs are a common site for metastasis to occur.
Synovial sarcoma can also spread to the brain, lymph nodes, and organs, and it becomes more difficult to treat successfully when it does. Prompt treatment early in the disease can reduce the risk of metastasis.
The joint mass of a synovial sarcoma may feel as if it is part of a muscle. As such, it can cause pain similar to muscle pain, and make it hard to use the affected joint.
So, people with synovial sarcoma in the legs may develop a limp, while a mass near the elbow can make it hard to use the arms.
Other symptoms of a synovial sarcoma include:
- Pain near the mass, though for some people, the mass is painless.
- Difficulties with functions near the mass, such as breathing if one is near the neck.
- Persistent, unexplained pain near a joint.
Early in the life of the tumor, some people mistake the mass for muscle swelling. They may attribute the pain to an injury or arthritis. So, any pain that does not go away after a few days should be discussed with a doctor.
Tests can diagnose synovial sarcoma. They include:
- Imaging scans of the affected area: These include magnetic resonance imaging (MRI) scans, computed tomography scans (CT), or X-rays. These scans are relatively simple and noninvasive procedures.
- A biopsy of the growth: During a biopsy, a doctor inserts a needle into the tumor to withdraw cells. Their appearance under a microscope can rule in or out a diagnosis of synovial sarcoma.
- Genetic testing: An abnormality between chromosome X and chromosome 18 is present in more than 90 percent of synovial sarcoma cases. Genetic testing can be done on the tissue sample obtained from biopsy.
- Bone scans: Complete blood count (CBC) and other blood tests may also be used.
This type of cancer has several treatment options that people can consider in discussion with their consultants.
When the tumor has clear margins, such that it can be removed alongside healthy tissue, the prognosis is best. It is important to remove some healthy tissue to reduce the chance of any cancer cells remaining.
Sometimes removing the entire tumor is difficult, particularly when it is located near a vital organ. On occasions, it may be necessary to amputate a limb to remove the tumor completely.
Chemotherapy, which uses potent chemicals and kills both cancerous and healthy cells, may be used. Chemotherapy can be helpful when the cancer has spread to other locations, or when a surgeon cannot remove the entire tumor.
A doctor may also recommend chemotherapy following tumor removal, to ensure the cancer does not return. Chemotherapy comes in many forms, including as a pill, an injection, and, as an intravenous (IV) drip.
Radiation therapy, like chemotherapy, kills cancer cells. It can be used alongside chemotherapy, after chemotherapy, or less frequently, as a standalone treatment. Radiation uses a specialized machine to target cancer cells with invisible high-energy beams.
Complications after treatment
Both radiation and chemotherapy can weaken the body, so anyone with synovial sarcoma may need additional treatments to remain healthy. Some drugs can reduce side effects. Occasionally, a person undergoing chemotherapy may need to be hospitalized to address complications.
Researchers are investigating experimental treatments to cure synovial sarcoma. Some individuals may be able to access clinical trials of these treatments, which include:
- Angiogenesis inhibitors: These drugs prevent the growth of the tumor and the development of new tumors, by blocking the development of blood vessels that support them.
- Biological therapies: This involves the use of drugs that support the body’s immune system to fight the cancer, or to reduce dangerous side effects of treatment.
Since cancer can metastasize, return, or grow slowly, doctors assessing cancer survival look at what percentage of people with it have survived at various points, following diagnosis.
At 5 years, the survival rate for synovial sarcoma is 50-75 percent. At 10 years, the rate is 40-60 percent. However, statistics about survival rates reveal little about an individual’s chances of being cured.
Many factors affect survival, including the size, age, grade, and location of the tumor. Overall health is relevant, as well, since people in good health are more likely to survive the treatment they receive.
Synovial sarcoma can reoccur even well after a person is in remission. Doctors have documented recurrences after 5 to 10 years, following removal of a tumor and remission. This suggests that continuing follow-up checks even many years after diagnosis and treatment are important for long term survival.
Because synovial cancer can recur, longer periods of remission are linked with greater chances of survival. So a person who survives 10 years following diagnosis has a higher chance of survival than someone who has survived a year.
What causes synovial sarcoma?
Unlike lung and some other cancers, which are linked to lifestyle factors, such as smoking, no lifestyle factors have been linked to synovial sarcoma.
The primary risk factor is the genetic anomaly that causes no other symptoms. The gene mutation that is thought to be responsible occurs between chromosome 18 and the X chromosome. Researchers do not know if it is something that happens randomly, or if it is something specific.
Some studies have found a link between radiation and environmental poisons and synovial and other soft tissue sarcomas. This link is not definitive, however.
Research also supports a link between some inherited conditions and synovial sarcoma. For example, people with Li Fraumeni syndrome and neurofibromatosis type 1 may have a greater risk of developing this cancer.