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Synovial sarcoma is a malignant soft-tissue sarcoma of uncertain histogenesis that arises near joints, tendon sheaths, or bursae.

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Epidemiology

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Despite the name, it does not originate from synovium but from pluripotent mesenchymal cells capable of epithelial differentiation.

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• Accounts for 5–10% of all soft-tissue sarcomas.
• Age: adolescents and young adults (15–40 years).
• Sex: slight male predominance.

Etiopathogenesis

• Genetic hallmark: translocation t(X;18)(p11;q11) resulting in SS18::SSX1/2 fusion gene.
• Leads to aberrant transcriptional activity and oncogenesis.
• Risk factors: none strongly established, unlike other sarcomas.

Sites:

• Para-articular regions of extremities (especially knee, ankle, foot).
• Can also occur in head–neck, thorax, retroperitoneum.

Pathology

https://doi.org/10.1038/modpathol.2009.47

• Gross: well-circumscribed, often multilobulated, may show areas of necrosis and hemorrhage.

Histological subtypes: