Chromogenic in situ hybridization using peptide nucleic acid probes: A promising adjunct to immunohistochemistry for identifying light chain restriction in multiple myeloma patients

Abstract

Chromogenic in situ hybridization (CISH) is a diagnostic tool that uses peptide nucleic acid probes (PNA) to recognize specific DNA/RNA sequences. It combines the in situ hybridization technology of fluorescence in situ hybridization (FISH) with chromogenic detection similar to immunohistochemistry (IHC). Assays were performed using DakoCytomation's (Carpinteria, CA) in situ hybridization kit with PNA κ and λ mRNA probes on bone marrow clot sections from 22 multiple myeloma patients. Two independent analytical methods were used to evaluate the CISH assayed slides for restriction after elimination of 5 suboptimal cases. Correlation between CISH and IHC results on the 17 remaining cases was 94%. Chromogenic in situ hybridization slides were easier to evaluate than IHC slides. The technical time required for the CISH staining protocol was comparable to that required for IHC. This pilot study established that the CISH protocol was capable of detecting restriction, was easier to interpret than IHC, and required technical time comparable to that required for IHC procedures.