Early detection of lymphomas in Sjögren's syndrome by in situ hybridisation for kappa and lambda light chain mRNA in labial salivary glands.

Sjögren's syndrome (SS) is an autoimmune disease characterised by a generalised lymphoproliferation. Patients have an increased risk of developing lymphomas which are usually of the type associated with mucosa-associated lymphoid tissue (MALT). Histological examination of the minor salivary glands of the lower lip is a common and useful diagnostic test for SS but has not been able to provide information with regard to potential malignant change. In this study, a sensitive in situ hybridisation technique for the detection of kappa and lambda immunoglobulin light-chain mRNA was applied to labial salivary glands of 14 patients with SS. 7 cases showed light chain restriction, in 5 cases this was kappa(kappa:lambda ratio > 8.0) and in 2 it was lambda(kappa:lambda ratio < 0.6). Of these 7, 5 developed lymphomas--4 were low grade lymphomas of MALT type and the fifth patient died of disseminated lymphoma. The finding of light chain restriction in lip minor salivary glands is strong evidence of a monoclonal population of B-cells at this site. It is concluded that in patients with SS who develop lymphomas, dissemination of malignant cells may result in detectable disease in the minor salivary glands. Determination of kappa:lambda ratios in labial minor salivary glands may thus provide important prognostic information.