In our study, massive B cells were found to be significantly infiltrated in the SGs of pSS by immune infiltration analysis, which is consistent with the high expression levels of MS4A1. In addition, complement receptor 2 (CR2/CD21) was located at follicular dendritic cell networks for the development of ectopic lymphoid structures in labial gland biopsies of patients with SS (Bombardieri and Pitzalis, 2012; Kurshumliu et al., 2019). This evidence concerns the gene MS4A1 and synovial sarcoma.