Ultrasensitive RNA in situ hybridization for detection of restricted clonal expression of low-abundance immunoglobulin light chain mRNA in B-cell lymphoproliferative disorders

To assess the feasibility of using a novel ultrasensitive bright-field in situ hybridization approach (BRISH) to evaluate κ and λ immunoglobulin messenger RNA (mRNA) expression in situ in B-cell non-Hodgkin lymphoma (NHL). A series of 110 semiconsecutive clinical cases evaluated for lymphoma with historic flow cytometric (FCM) results were assessed with BRISH. BRISH light chain restriction (LCR) results were concordant with FCM in 108 (99%) of 109 evaluable cases. Additional small B-cell lymphoma cohorts were successfully evaluated. BRISH analysis of κ and λ immunoglobulin mRNA expression is a sensitive tool for establishing LCR in B-cell NHL when FCM results are not available.