CALR and synovial sarcoma: A controversial question is whether retroviruses (including human T-cell leukemia virus [HTLV-1] [1,2,3,4], human immunodeficiency virus [HIV] [5,6,7], Epstein–Barr virus [EBV] [8,9], and hepatitis C virus [HCV] [10,11,12]) and/or cytomegalovirus [13,14] are candidate causes of Sjögren’s syndrome (SS), which is an autoimmune disease exhibiting sialadenitis, the appearance of autoantibodies including anti-Ro/SS-A, La/SS-B antibodies, and extraglandular manifestations [15,16,17].