HIGH-FREQUENCY OF LIGHT-CHAIN RESTRICTION IN LABIAL GLAND BIOPSIES OFSJOGRENS-SYNDROME DETECTED BY IN-SITU HYBRIDIZATION

A well-recognized complication of Sjogren's syndrome (SS) is the devel opment of malignant lymphoma, with a risk 44 times that of the general population. Although a few clinical signs may indicate the onset of l ymphoma, there are few reliable laboratory markers which predict the d evelopment of neoplasia. A non-isotopic in situ hybridization techniqu e has been applied to routinely processed labial salivary gland (LSG) biopsies of patients under investigation for SS. Serial sections of 70 LSGs were examined for kappa re and lambda immunoglobulin light chain mRNA using digoxigenin-labelled oligonucleotide probes. As controls, 39 biopsies from non-SS-associated sialadenitis were also examined. Se ctions were analysed using computer-assisted quantification to determi ne the percentage of kappa-expressing cells in each case. The range of kappa expression in the SS group was 24.1-93.4 per cent and in the no n-SS group 48.3-75.4 per cent. Light chain restriction was found in 13 /70 (18.6 per cent) cases from the SS group but in no cases of the con trol group. Of the SS cases showing restriction, 4/13 (30.7 per cent) have subsequently developed extrasalivary gland lymphoma. Two patients not showing light chain restriction in LSG have subsequently develope d lymphoma. The positive predictive value of this test to identify pat ients at risk of lymphoma was 30.7 per cent with a detection rate (sen sitivity) of 66.7 per cent and a false-positive rate of 14.1 per cent (specificity 85.9 per cent). This study has identified a high prevalen ce of light chain restriction in labial gland biopsies of patients wit h SS and provides objective quantitative criteria to identify those pa tients at greater risk of lymphoma development.