Hematogones with Light Chain Restriction: A Potential Diagnostic Pitfall When Using Flow Cytometry Analysis to Assess Bone Marrow Specimens

Abstract Light-chain restricted hematogones (LCR HGs) detected by flow cytometry analysis can mimic bone marrow involvement by B-cell lymphoma. This phenomenon can present a diagnostic pitfall and negatively impact patient management, as misinterpretation may upgrade disease stage. In this study, we characterized the immunophenotype of LCR HGs with an aim to differentiate them from B-cell lymphoma. We analyzed 24 patients with LCR HGs, 12 (50%) were kappa light chain restricted and 12 (50%) were lambda light chain restricted. LCR HGs account for 51% (range, 1.5% to 99%) of B cells, and 0.5% (range, 0.1% to 3.7%) of total cells. In 15 patients in whom multiple specimens were analyzed, 10 (67%) showed persistent LCR HGs in more than 1 specimen, and the duration of the light chain restriction ranged from 4 months to 2 years. Among 24 patients, 4 (16.6%) cases were concurrently involved by B-cell lymphoma/myeloma in addition to LCR HGs. With the exception of light chain restriction, LCR HGs showed a similar immunophenotype as normal HGs and had a distinct location on the CD45/Side Scatter (SSC) plot. They were also consistently positive for CD10, CD19, CD38 (bright), CD43, and CD200. CD20 expression showed a spectrum from dim/negative to positive.