B-cell lymphoma accompanying monoclonal macroglobulinemia with features suggesting marginal zone B-cell lymphoma

Waldenstroem's macroglobulinemia is usually closely related to a histopathologic subtype called lymphoplasmacytoid lymphoma in the Revised European-American Lymphoma (REAL) classification. Here, we report a case of B-cell lymphoma accompanied by monoclonal macroglobulinemia and pathologically compatible with marginal zone B-cell lymphoma (MZBCL) rather than lymphoplasmacytoid lymphoma. The patient was a 74-year-old man with lymphomatous lesions that were recognized as submandibular lymphadenopathy, subcutaneous tumor and bilateral orbital masses, but with no bone marrow involvement. The atypical lymphoid cells that occupied the lymph node were varied such as small cells harboring irregular nuclei, monocytoid B-cells, large cells with vesicular nuclei, and plasma cells. The tumor cells expressed CD19, CD20, IgM and kappa on their cell surfaces and cytoplasmic IgM, but not CD5 or CD10. These findings suggest that the clinical and histopathologic findings of this case are compatible with those of MZBCL rather than lymphoplasmacytoid lymphoma. Serum IgM was elevated up to 4080 mg/dl and M-proteinemia of IgM-kappa type was confirmed by immunoelectrophoresis. Hyperviscosity syndrome caused by monoclonal IgM was not apparent. Immunohistochemical study confirmed that monoclonal IgM-kappa was produced and secreted from the tumor cells of MZBCL. This case suggests a close relationship between MZBCL and lymphoplasmacytoid lymphoma, from the perspective of the cellular origin during B-cell differentiation.