Synovial sarcoma is a rare and aggressive type of cancer that primarily affects soft tissues. This malignancy can emerge in various parts of the body, including muscles, tendons, ligaments, and fat. While it often develops near joints, such as the knee or shoulder, it does not originate from the synovial cells lining the joints themselves. Synovial sarcoma accounts for approximately 5% to 10% of all soft tissue sarcomas.
The Defining Genetic Anomaly
The primary cause of synovial sarcoma is a specific genetic alteration known as a chromosomal translocation. This involves a rearrangement of genetic material between chromosome X and chromosome 18. Specifically, a segment of the SYT gene on chromosome 18 fuses with one of the SSX genes, most commonly SSX1 or SSX2, located on chromosome X.
This resulting SYT-SSX fusion gene is a consistent characteristic found in over 90% of all synovial sarcoma cases. This fusion gene is the defining genetic signature and primary driving force behind the cancer’s development. This genetic change is typically spontaneous, occurring during a person’s lifetime within specific cells rather than being inherited.
Understanding Risk Factors
Unlike many other cancers, synovial sarcoma does not have well-established external or environmental risk factors. There is no clear evidence linking its development to lifestyle choices, specific chemical exposures, or radiation exposure.
The SYT-SSX fusion gene is almost always acquired somatically, meaning it arises in body cells after conception rather than being present in germline cells. Consequently, synovial sarcoma is not considered a hereditary cancer that can be passed down through families. Research has also indicated that prior injury or trauma to an area has not been definitively linked as a causative factor.
How the Genetic Change Drives Cancer
The SYT-SSX fusion gene produces an abnormal protein that disrupts normal cellular functions. This fusion protein acts as an aberrant transcription factor, improperly regulating the expression of other genes within the cell. By interfering with gene expression, the protein can activate genes that promote cell growth and division while suppressing genes that control normal cell differentiation and programmed cell death.
This dysregulation leads to uncontrolled cell proliferation, where cells divide rapidly and without the usual checkpoints that regulate healthy tissue growth. The interference with differentiation pathways can cause the cells to remain in an immature state, contributing to their cancerous properties. These mechanisms, driven by the SYT-SSX fusion protein, result in the formation and progression of a synovial sarcoma tumor.