Rapid in-situ hybridization and immunohistochemistry: a pilot comparative study of two rapid diagnostic techniques for establishing monoclonality in plasma cell dyscrasias

BackgroundLight chain restriction needs to be established on the paraffin embedded tissue in certain types of plasma cell dyscrasias when serum levels of monoclonal immunoglobulins and light chain assays in the urine and serum may be normal. Rapid-in-situ-hybridisation (RISH) is thought to be a superior to immunohistochemistry (IHC) for kappa and lambda staining due to brighter and crisp staining without any background.MethodsFifty cases were included in this pilot study. Serum light chain restriction status of the case was taken as gold standard. The results of standard IHC for kappa and lambda immunoglobulins on the bone marrow biopsy of these cases was compared with RISH performed by the two commercially available kits. The results of the two methods were compared for sensitivity, need to repeat the test and background staining.ResultsThe study found that in IHC first run sensitivity was 58% which improved to 88% after the second run. For RISH the sensitivity was 100%.ConclusionRapid-in-situ-hybridisation (RISH) is a superior technique to IHC for detecting kappa and lambda light chain in plasma cells. The test is as labour intensive and time consuming as the routine IHC but has no background staining with more bright and crisp staining quality.