Among the TGF-β isoforms (TGF-β1, -β2, and -β3), TGF-β1 plays a crucial role in the pathogenesis of SS. A study has shown that the expression level of serum TGF-β1 in SS patients increases significantly with the aggravation of disease severity [53]. This may be related to the pro-fibrotic effect of TGF-β1. The gene discussed is TGFB1; the disease is synovial sarcoma.