IL-21, IFN-γ and IL-21/IFN-γ-producing CXCR5+ICOS+PD-1+ Tfh-cells (figure 1O–Q), but also total CXCR5+ICOS+PD-1+ Tfh-cells (online supplementary figure S2K) closely correlated with the SG focus score while circulating CXCR5+CD4+ T-cells double expressing ICOS+PD-1+ were higher in patients with SS with ELS (figure 1R and online supplementary figure 2L, M, P). Here, IL21 is linked to synovial sarcoma.