TNFSF13B and synovial sarcoma: In contrast, other studies showed that B-cell activation in the ectopic germinal center (GC) was also mediated by C-X-C motif chemokine 13 (CXCL13), and that B-cell activating factor of the tumor necrosis factor (TNF) family (BAFF) is also involved in the pathology of SS [15,16,17].