Synovial Sarcoma

Synovial sarcoma, also known as malignant synovioma, is a rare type of sarcoma (cancer arising from bones and/or soft tissue) that develops in the soft tissue surrounding joints in the body. It is named for its resemblance to synovial tissue, which is generally found around tendons (connective tissue that connects muscle to bone) and helps to keep joints lubricated. Despite its name, synovial sarcomas do not develop from synovial tissue.

In most cases, synovial sarcomas are found next to large joints in the body, such as the knees. They are also commonly found in the head, neck, arms, and legs. In rare cases, they may develop from soft tissue in the abdomen, lung, bladder, and vagina.

Synovial sarcomas are more common in males, and tend to be diagnosed in teenagers and young adults. However, anyone can develop this disease.

Types of Synovial Sarcoma

There are four primary types of synovial sarcoma, which are classified by their cellular appearance under the microscope.

Biphasic Synovial Sarcoma

Biphasic synovial sarcoma is a less common subtype of synovial sarcomas that have two types of cells in the tumour called spindle cells and epithelial cells. These tumours are often aggressive, likely to metastasise, and can have a good prognosis when found early.

Monophasic Fibrous Synovial Sarcoma

Monophasic fibrous synovial sarcomas are the most common type of synovial sarcomas that contains only spindle cells within the tumour. These tumours are often aggressive, likely to metastasise, and can have a good prognosis when found early.

Monophasic Epithelial Synovial Sarcoma

Monophasic epithelial synovial sarcoma is a very rare subtype of synovial sarcoma that contains only epithelial cells within the tumour. This type of tumour is often misdiagnosed for adenocarcinomas, which are cancers arising from mucus-producing glands in organs. There is limited information on the aggressiveness and prognosis of this subtype.

Poorly Differentiated Synovial Sarcoma

Poorly differentiated synovial sarcomas are a less common type of synovial sarcoma with varying cellular components. These tumours are often aggressive, likely to metastasise, and can have a good prognosis when found early.

Treatment

If a synovial sarcoma is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.

Cancers can be staged using the TNM staging system:

  • T (tumour) indicates the size and depth of the tumour.
  • N (nodes) indicates whether the cancer has spread to nearby lymph nodes.
  • M (metastasis) indicates whether the cancer has spread to other parts of the body.

This system can also be used in combination with a numerical value, from stage 0-IV:

  • Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
  • Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
  • Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
  • Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
  • Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.

Cancers can also be graded based on the rate of growth and how likely they are to spread:

  • Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
  • Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
  • Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.

Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.

Treatment is dependent on several factors, including location, stage of disease and overall health.

Treatment options for synovial sarcomas may include:

  • Surgery to remove as much of the tumour as possible.
  • Radiation therapy.
  • Chemotherapy.
  • Clinical trials.
  • Palliative care.

For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.

Risk factors

Because of how rare synovial sarcomas are, there has been limited research done into the risk factors of this disease.

Symptoms

Synovial sarcomas may appear asymptomatic in the early stages of disease. As the tumour progresses, the following symptoms may appear:

  • A mass that may be painful or painless.
  • Bleeding from the nose, vagina, rectum, or throat (if the tumour is in the area).
  • Tingling, numbness, and/or pain in affected area if the tumour is compressing a nerve.
  • Eye bulging (if tumour is behind eye).
  • Drooping of the eyelid (if tumour is behind the eye).

Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.

Diagnosis/diagnosing

If your doctor suspects you have a synovial sarcoma, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment.

Physical examination

Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.

Imaging & blood tests

The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.

Biopsy

Once the location(s) of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. The tissue sample will then be analysed for cancer cells. This can be done by a fine needle aspiration (FNA) or a core needle biopsy (CNB).

References

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