A 65-year-old woman is found to have an IgM paraprotein of 3.2 g/dL, bone marrow showing >10% lymphoplasmacytic cells, and splenomegaly. She does NOT have lytic bone lesions. What is the most likely diagnosis?

• A Waldenström macroglobulinemia ✓
• B Multiple myeloma (IgM type)
• C Marginal zone lymphoma with plasmacytic differentiation
• D Monoclonal gammopathy of undetermined significance (MGUS)

Explanation

Waldenström macroglobulinemia is a lymphoplasmacytic lymphoma that secretes IgM, causing hyperviscosity, splenomegaly/hepatomegaly/lymphadenopathy, and cytopenias, but characteristically lacks the osteolytic bone lesions and hypercalcemia typical of multiple myeloma. The diagnostic criteria require >10% lymphoplasmacytic cells in the bone marrow and a serum IgM monoclonal protein of any level. The MYD88 L265P mutation is present in >90% of cases and helps distinguish it from other B-cell lymphomas. MGUS has <10% bone marrow plasma/lymphoplasmacytic cells.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.