Synovial sarcoma

Synovial sarcoma Definition

It is a serious disorder characterized by a malignant tumor around certain joints of the body. It is a type of soft-tissue sarcoma that develops in connective tissues. The disorder most often occurs in adolescents or young adults, especially males. Malignant synovioma is the other name of the condition.

Synovial sarcoma Symptoms

The tumor primarily occurs near the large joints of the arms, legs and knees. However, the tumor may also appear as an abnormal swelling or mass in the heart, brain, or prostrate gland. The location of the malignant lesion determines the symptoms of the condition. Neurological involvement may give rise to severe pain. Patients may have difficulty swallowing, breathing or speaking if the sarcoma affects the head and neck region. In rest of the cases, the condition is asymptomatic due to the slow-growing nature of the tumor.

Synovial sarcoma Causes

Although some of these tumors resemble synovium, a thin membrane in synovial joints that lines the joint capsule, it has never been shown to originate from synovial cells. The exact cause of the condition is not entirely understood, however, research has indicated that specific genetic defects may play a role. It is most likely that certain portions of chromosome 18 and chromosome X have switched places in the tumor cells. It is not known whether this mutation occurs randomly or follows a specific chain of events. Simply put, the presence of a mutant gene is attributed to chromosomal translocation.

Synovial sarcoma Histopathology

As aforementioned, the translocation event between the SS18 gene on chromosome 18 and one of 3 SSX genes (SSX1, SSX2 and SSX4) on chromosome X causes the presence of a SS18-SSX fusion gene. The fusion protein on being released binds the transcriptional activating domain of SS18 to the transcriptional repressor domains of SSX. Dysregulation of gene expression due to the formation of SS18-SSX is responsible for the development of the disorder. Microscopic examination of the malignant tumor has revealed the following two types of cells:

  • Fibrous/Spindle/Sarcomatous: These cells are small, uniform, and arranged in sheets.
  • Epithelial: The cells are compact and tightly packed.

In some instances, the cells are not properly differentiated, or may only comprise of sheets of spindle cells. However on very rare occasions, there can be a monophasic epithelial form.

Synovial sarcoma Diagnosis

Painless as well as deep-seated tumors may often go unnoticed for a long time, and do not receive timely diagnosis. Healthcare providers usually evaluate the abnormal mass by conducting the common imaging tests like:

  • X-ray
  • Sonogram
  • Computed Tomography
  • Magnetic resonance imaging

Once the presence of a lump near the joints is confirmed, a biopsy of the tumor may aid in further analysis of the disorder. Doctors generally prefer an open biopsy in which a surgical incision is made to remove the sample. However, core needle biopsy could also be considered as a less invasive procedure. Differentiating the disorder from other forms of sarcoma is however, challenging. The sample tissue obtained from the biopsy is typically used for immunohistochemistry, a clinical technique in which the antigens or proteins in the malignant tissues are localized by the use of labeled antibodies as specific reagents. Visualization of the antigen-antibody interactions with the help of a marker such as fluorescent dye, enzyme, or colloidal gold provides additional information about the tumor. For greater visibility, the sample tissue is normally stained with different dyes. However, cytogenetic studies remain the gold standard test for confirming malignant synovioma. This specialized test shows a translocation between the X chromosome and chromosome 18 in the tumor cells. Once the degree of malignancy of the tumor is known, further imaging studies such as a PET scan of the whole body and/or CT scan of the chest, abdomen or pelvis can be done to look for possible metastases.

Synovial sarcoma Treatment

The severity of the disorder determines the exact course of treatment and management. Healthcare givers usually consider some essential factors that are specific to the patient before initiating any therapeutic measure. Some of these are:

  • Size of the tumor
  • Aggressiveness of the disease
  • Degree and location of metastases
  • Involvement of the lymph nodes

After obtaining the required information, physicians may implement any one of the following treatment methods:


Administration of chemotherapeutic agents like doxorubicin hydrochloride and ifosfamide can destroy the cancer cells and prevent the disease from spreading to other parts of the body. Chemotherapy also increases the survival rate in patients with invasive form of the tumor.


In this technique, high ionizing rays are used to damage the malignant cells for lowering the risk of local recurrence. However, the curative effects of radiation treatment on the tumor are not well identified.


Aggressive tumors need to be excised with clear margins. This can be achieved when healthy tissues surrounding the abnormal lump are eradicated along with it. In this way, the doctors can make sure that the cancer cells have been removed from the affected region. Depending on the location and size of the malignant mass, it may be however, quite challenging for a specialist to remove adequate margins around the tumor while preserving the biological functions. Radiotherapy is often used as an additional method, before or after the surgery, in order to reduce the risk of leaving the cancerous cells behind.

Synovial sarcoma Prognosis and Survival Rate

The outlook of patients with malignant synovioma is completely based on certain statistics study conducted on them. Although the analytical study cannot predict the future of an ailing patient, it can determine the most appropriate treatment. Prognosis is always influenced by the severity of the disease. Patients with small tumors have an excellent prognosis as these can be completely removed with adequate margins. However, the risk of developing distant metastases is higher for patients with larger lesions. Affected individuals with irremovable metastatic growths also have a poor prognosis.

Synovial sarcoma is a rare form of cancer, and only 1 to 3 individuals in a million are diagnosed with this condition every year. Survival rates have improved in the past 20 years due to the availability of a variety of therapeutic procedures. Regular follow-up is a must, which involves clinical examination, MRI of the surgical site, and CT scan of the chest.

Synovial sarcoma in Dogs

Large breed dogs are more susceptible to this type of sarcoma than the smaller breeds. Aggressive tumors can be more fatal as the disease often spreads to the lymph nodes ands invade various parts of the animal’s body. Swelling, pain and lameness in the affected joint are some of the common symptoms experienced by the dogs.


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