Dual Surface Immunoglobulin Light-Chain Expression in B-Cell Lymphoproliferative Disorders

Abstract

Abstract Context.—Mature B lymphocytes exhibit allelic exclusion in which only a single class of immunoglobulin heavy chain and a single class of light chain, either κ or λ, are expressed. There have been several reports indicating that double light-chain gene rearrangements or dual light-chain expression can occur in B-cell malignant neoplasms, including chronic lymphocytic leukemia. Currently, it is a common notion that demonstration of light-chain restriction in a B-cell population is generally considered proof of monoclonality and indicates malignancy. Objective.—To increase awareness of the existence of the dual κ/λ immunoglobulin light-chain expressing B-cell leukemia/lymphoma, to emphasize the importance of visual inspection of flow cytometric data, and to present the guidelines for flow cytometric interpretation of dual κ/λ coexpressing populations. Data Sources.—Through comprehensive literature review, this article discusses the current understandings regarding the dual light-chain expression in B-cell neoplasms, the cellular and molecular mechanisms, and the clinical and diagnostic implications of dual light-chain expression. Conclusions.—Dual κ/λ light-chain expressing B-cell leukemia/lymphomas do exist. Recognition of the dual κ/ λ light-chain expression on B cells has diagnostic implication in leukemia/lymphoma immunophenotyping.