BACKGROUND Non-
IgM lymphoplasmacytic
lymphoma (LPL) is a rare subtype of LPL, constituting less than 5% of the cases, and is often associated with
IgG,
IgA, or light chain
paraproteins and is rarely a non-secretor. Non-
IgM LPL remains poorly studied, and the differential diagnosis from other small
B-cell lymphomas with plasmacytic differentiation and
plasma cell neoplasm is challenging. CASE REPORT A 67-year-old woman presented with
weight loss, persistent
anemia, and borderline
leukopenia.
Serum protein electrophoresis and immunofixation demonstrated a faint
IgG and kappa band against a dense polyclonal background. Bone marrow biopsy revealed hypercellular marrow with involvement by abnormal B cells with undetectable surface and cytoplasmic
immunoglobulin light chains. Interestingly, these B cells showed no expression of light chains or production of
IgG and
IgM; however, they showed production of intracytoplasmic
IgA. The concomitant neoplastic plasma cells also displayed no definitive light chain expression. Both IgH and
IgK gene rearrangements were positive for clonal process. Molecular studies showed positive MYD88 L265P mutation and CXCR4 mutation (c.1013C>G). The overall findings confirmed marrow involvement by non-
IgM LPL. The patient received 6 cycles of
rituximab and
bendamustine treatment, and no residual marrow involvement was found on the follow-up bone marrow biopsy. CONCLUSIONS We report a non-
IgM LPL case featuring no light chain production and no heavy chain secretion, which we believe is the first reported case of this kind in the literature.