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Introduction: Lymphoplasmacytic lymphoma (LPL) is a rare low-grade B-cell neoplasm that accounts for approximately 2% of all haematological malignancies. Most patients have the clinical syndrome of Waldenstrom macroglobulinemia (WM), which is defined as LPL with an associated immunoglobulin M (IgM) serum monoclonal protein. Roughly 5% of LPL patients secrete non-IgM paraproteins (e.g., IgG, IgA, kappa, lambda) or are non-secretory.

Case description: We report the case of a 41-year-old woman who was diagnosed with non-IgM LPL with lambda light chain monoclonal paraprotein production and normal serum immunoglobulin levels. The MYD88 L265P mutation was detected on fluorescence in-situ hybridization (FISH) analysis of the bone marrow. The patient underwent treatment with a combination of ibrutinib and rituximab. There was an initial response but she died 8 months after diagnosis.   

Discussion: Non-IgM LPL poses diagnostic and therapeutic challenges to clinicians as it is an exceptionally rare malignancy with a heterogeneous clinicopathological presentation and scarce literature. Among non-IgM LPL cases, those with lambda light chain production are even more rare. To the best of our knowledge, none have been reported to date. The addition of MYD88 L265P testing to the diagnostic armamentarium of non-IgM LPL cases is advisable for potential therapeutic reasons.