Definition and Overview

Synovial sarcoma is one of the many types of soft tissue sarcomas (STS) or cancers that begin in soft tissue, such as nerves, tendons, fats, muscles, and blood vessels. As a group, STS is very rare, accounting for just about 1% of all cancer cases.

Synovial sarcoma affects just about 900 people (mostly teenagers and young adults) in the United States every year. It is a high-grade, aggressive tumour that is known to spread to other parts of the body (metastasis). Despite its name, it is not related to the part of the joints called synovial tissues. It starts in primitive mesenchymal cells and usually presents with deep-seated, painless mass that grows rapidly. In some cases, the condition can limit range of motion and cause pain if the tumour is pressing on nearby nerves.

Synovial sarcoma commonly develops in lower extremities but can also occur in the trunk, head, neck, and lungs. It is generally associated with a history of a small, painless nodule that has rapidly increased in size.

The prognosis for patients with synovial sarcoma is generally fair. The 5- and 10-year survival rates are 50-60% and 40-50%, respectively. However, survival rates continue to improve with aggressive treatment that combines primary radical surgery, radiation, and chemotherapy.

Causes of Condition

Just like other soft tissue sarcomas, the exact cause of synovial sarcoma is not fully understood. However, research suggests that genetic alternations may play a role in its development. In up to 90% of cases, a rearrangement in the chromosome material between chromosomes 18 and X is observed. This rearrangement changes the function and position of genes, resulting in fusion transcript that creates a new, novel gene.

People with the following conditions are also found to have an increased risk of developing synovial sarcoma:

  • Neurofibromatosis - A genetic disorder that affects nerve cell tissue development. Tumours called neurofibromas typically develop on nerves and alter the function of NF1 gene, which increases the risk of synovial sarcoma.

  • Li-Fraumeni syndrome - A rare inherited genetic cancer disorder that increases a person’s risk of developing malignant tumours. The condition affects p53 (a gene that functions as a tumor suppression) function, which increases the risk of soft tissue sarcoma.

Some studies also suggest that exposure to carcinogens and radiation therapy also increase the risk of soft tissue sarcoma.

Key Symptoms

In the early stages, synovial sarcoma presents as a slow-growing and painless deep-seated mass. As the tumour grows bigger, it causes swelling and a noticeable lump that may or may not cause pain, numbness, and limited range of motion.

Other symptoms may also develop depending on the tumour’s size and anatomical location and whether or not the cancer has already spread to other organs. Patients may cough up blood or suffer from pneumothorax if cancer spreads to the lungs, which are the most common sites of spread or metastasis. If cancer spreads to the bones, symptoms will include bone pain and fractures. It is also possible for patients to suffer from gastrointestinal symptoms if the abdomen, liver or pelvis has been affected.

Who to See and Types of Treatments Available

Synovial sarcoma can be diagnosed with the following tests and procedures:

  • Genetic testing - Used to detect chromosomal translocation between chromosome X and chromosome 18.

  • X-rays - Typically the first imaging test used to obtain pictures of internal organs, tissues, and bones. X-rays can show soft tissue tumours and provide information that helps doctors determine if they are cancerous or benign. Based on the results of x-rays, doctors may order confirmatory imaging tests.

  • Magnetic resonance imaging (MRI) and computed tomography (CT) scan - Used to confirm the presence of mass as well as its size and location. A CT scan of the chest is also performed to determine if cancer has already spread to the lungs.

  • Bone scans - Used to determine the cause of bone pain and fracture.

  • Open or core needle biopsy - Involves obtaining sample tissue for further analysis.

The above tests are useful in:

  • Confirming a synovial sarcoma diagnosis

  • Determining the stage cancer

  • Determining the most appropriate course of treatment

Treatment

The primary treatment for synovial sarcoma is the surgical removal of the entire tumour along with a wide margin of healthy tissue surrounding it. This must be performed while ensuring that the function of the affected body part will not be impaired after the operation. Radiotherapy or chemotherapy may be administered before or after surgery. They are administered before the operation if the tumour has become very large that it cannot be safely removed with surgery. If administered after the procedure, their goal is to kill remaining cancer cells to prevent recurrence.

As much as possible, surgeons use a technique that aims to save the affected limb (limb-saving operation). However, in some cases, amputation may be necessary depending on the tumour’s size and location. The procedure is often followed by postoperative radiation therapy, which is especially crucial if the margins are close to vital neurovascular structures. The most commonly used method is external beam radiation (EBT) where beams generated from outside the patient’s body are targeted at the tumour site.

Prior to initiating any form of cancer treatment, patients are advised about its risks and possible complications, which may include:

  • Adverse reaction to the anaesthetic use

  • Infection

  • Neurologic or vascular injury

  • Pulmonary embolism

  • Seroma formation

  • Severe bleeding

  • Wound breakdown

  • Wound infection

Following successful treatment, patients are monitored with regular check-ups and periodic evaluations, which often include the use of imaging tests. They are advised to consult their doctor every 3-6 months for the first two years and then every six months for the next three years. The goal of long-term monitoring is to catch the early signs of metastasis so appropriate treatment can be promptly initiated.

References:

  • Zagars GK, Ballo MT, Pisters PW, Pollock RE, Patel SR, Benjamin RS, et al. Prognostic factors for patients with localized soft-tissue sarcoma treated with conservation surgery and radiation therapy: an analysis of 1225 patients. Cancer. 2003 May 15. 97(10):2530-43.

  • Ladanyi M, Antonescu CR, Leung DH, Woodruff JM, Kawai A, Healey JH, et al. Impact of SYT-SSX fusion type on the clinical behavior of synovial sarcoma: a multi-institutional retrospective study of 243 patients. Cancer Res. 2002 Jan 1. 62(1):135-40.

  • Terasaki H, Niki T, Hasegawa T et-al. Primary synovial sarcoma of the lung: a case report confirmed by molecular detection of SYT-SSX fusion gene transcripts. Jpn. J. Clin. Oncol. 2001;31 (5): 212-6. doi:10.1093/jjco/hye045

  • Krieg AH, Hefti F, Speth BM et-al. Synovial sarcomas usually metastasize after >5 years: a multicenter retrospective analysis with minimum follow-up of 10 years for survivors. Ann. Oncol. 2011;22 (2): 458-67. doi:10.1093/annonc/mdq394

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