Artifactual Kappa Light Chain Restriction of Marrow Hematogones: A Potential Diagnostic Pitfall in Minimal Residual Disease Assessment of Plasma Cell Myeloma Patients on Daratumumab. Issue 1 (17th July 2019)

• Record Type: Journal Article
• Authors: Jiang, Xiu yan; Luider, Joanne; Shameli, Afshin
• Is Part Of: Cytometry. Volume 98:Issue 1(2020)
• Page Start: 68
• Page End: 74
• Publication Date: 2019-07-17
• Subjects: plasma cell myeloma -- daratumumab -- hematogones -- light chain restriction; Flow cytometry -- Diagnostic use -- Periodicals; Cytodiagnosis -- Periodicals; 616.07582
• DOI: 10.1002/cyto.b.21837
• Languages: English
• ISSNs: 1552-4949

Abstract

Abstract : Background: Daratumumab (DARA) is a humanized Immunoglobulin G(IgG)1‐kappa monoclonal antibody against CD38 antigen that is shown to improve outcomes in relapsed/refractory plasma cell myeloma (PCM) patients. Since CD38 is expressed by different hematopoietic elements, DARA has the potential to interfere with flow cytometric assessment of bone marrow specimens. Methods: Flow cytometric analysis of bone marrow samples from 10 PCM on DARA and 5 control samples was performed using two different antibody panels. Results: Bone marrow samples from PCM patients on DARA exhibited a population of CD19+ CD10+ B‐lymphoid cells with kappa light chain restriction. Further morphological and immunophenotypic studies suggested that this population represents marrow hematogones. Marrow hematogones from control samples showed normal immunophenotypic profiles. Conclusion: DARA on the surface of hematogones interferes with flow cytometric clonality study leading to artifactual kappa light chain restriction, which can result in false interpretation of a concurrent clonal B‐cell proliferation. In the era of rapidly growing list of therapeutic monoclonal antibodies, flow cytometry pathologists should be aware of potential interferences to avoid misdiagnosis. © 2019 International Clinical Cytometry Society