Mature B lymphocytes exhibit allelic exclusion in which only a single class of immunoglobulin heavy chain and a single class of light chain, either kappa or lambda, 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.
To increase awareness of the existence of the dual kappa/lambda 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 kappa/lambda coexpressing populations.
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.
Dual kappa/lambda light-chain expressing B-cell leukemia/lymphomas do exist. Recognition of the dual kappa/lambda light-chain expression on B cells has diagnostic implication in leukemia/lymphoma immunophenotyping.