Recent studies revealed that B cell-activating factor-receptor (BAFF-R) His159Tyr mutation and a tumor necrosis factor, alpha-induced protein 3 (TNFAIP3) germline coding variation—both associated with the activation of the NF-κB pathway—are important contributors in primary SS and SS-related lymphomagenesis [11–16]. Here, TNFRSF13C is linked to synovial sarcoma.