CALR and synovial sarcoma: In SS, no key epitope(s) are identified, although several proteins have been implicated as a source of antigens: Ro/SSA 52 kDa, αFodrin, Muscarinic Acetylcholine 3 Receptor (M3R), α-amylase, islet cell autoantigen-69, kallikrein-13 [19]–[24].