IN-SITU HYBRIDIZATION ANALYSIS OF LYMPHOPROLIFERATIVE DISORDERS - ASSESSMENT OF CLONALITY BY IMMUNOGLOBULIN LIGHT-CHAIN MESSENGER-RNA EXPRESSION

Determination of clonality in B-cell lymphomas is a useful diagnostic adjunct. In situ hybridization (ISH) for the detection of kappa and la mbda mRNAs has the potential to overcome some common specimen-related limitations in clonal assessment. Tritium-labeled antisense cRNA probe s directed at conserved segments of the constant regions of the kappa and lambda mRNAs were used in an autoradiographic method to detect B-c ell clonality. Using these probes, we analyzed 103 formalin-fixed, par affin-embedded biopsy samples, and the results were subsequently compa red to available immunophenotypic (all cases) and genotypic (50 cases) data. Of 103 samples, 82 (80%) had adequate RNA preservation as deter mined by actin RNA signals, and 73 (89%) of the 82 cases demonstrated concordant clonality assignment by both ISH and immunophenotyping. The remaining nine cases showed a specific form of discordance in that ea ch exhibited no protein (Ig) expression but had evidence of mRNA immun oglobulin light-chain expression. Forty-five (90%) of 50 cases evaluat ed for immunoglobulin and T-cell receptor beta-gene rearrangements dem onstrated concordant results with respect to clonality assignment by I SH. Thus, ISH demonstrates adequate sensitivity with respect to tradit ional methods of clonality assessment. However, its practical utility awaits the development of nonradioactive detection methods with adequa te sensitivity to improve turnaround time.