The limitations of this study are that it is a case-control study, the salivary gland biopsy ectopic germinal-like structures and focus scores, serum cryoglobulins, and serum beta-2 microglobulins were not evaluated, and the number of patients in some lymphoma predictor subgroups such as parotid gland swelling and purpura were insufficient. This evidence concerns the gene B2M and purpura.