Hematogones and Light Chain Restriction – Diagnostic Dilemma

Abstract: Examination of bone marrow (BM) involvement is essential for staging and prognostication in non-Hodgkin lymphoma, such as diffuse large B-cell lymphoma (DLBCL). This can be evaluated by BM aspiration, biopsy and flow cytometry (FCM) as these are complementary to each other. Hematogones present in BM can resemble disease-related BM involvement if not analyzed carefully. In addition, analysis by FCM can be complicated if rituximab is used for treatment. Rituximab is anti-CD20 antibody, and it can lead to the absence of late-stage II and stage III hematogones, disrupting the typical maturation pattern associated with these cells. Hematogones are immature B-cell precursors with a distinctive immunophenotype profile on FCM, typically lacking surface immunoglobulin light chain expression. However, limited literature exists regarding the expression of surface light chains by hematogones. Here, I present a rare case of hematogones exhibiting surface light chain expression, highlighting the diagnostic challenges in assessing BM involvement in DLBCL through FCM-based immunophenotyping, particularly in patients receiving rituximab.