IL17A and synovial sarcoma: Th1 and Th17 cytokines are implicated in the pathogenesis of SS; although results are variable, Th1 cytokines (e.g. interferon-γ (IFN-γ), interleukin (IL)-2) and Th17 cytokines (e.g. tumor necrosis factor (TNF)-α and IL-17) are highly expressed in SS patients [2, 3].