Molecular Analysis in a Patient With Waldenström's Macroglobulinemia Reveals a Rare Case of Biclonality

Background: The immunoglobulin and T-cell receptor gene rearrangement test is used to identify monoclonal populations in B- and T-cell malignancies and has become an important adjunct to morphologic analysis and immunophenotyping by flow cytometry. Waldenström's macroglobulinemia (WM) is typically a monoclonal proliferation of B cells with morphology of plasmacytoid lymphocytes and production of monoclonal IgM. Methods and Results: We report a case of WM with biclonal gammopathy (IgM kappa and IgM lambda) involving the blood and a diffuse lymphoplasmacytic infiltrate in the bone marrow in an 83-year-old man. Immunophenotyping of the blood and bone marrow aspirate revealed B cells expressing IgM lambda surface immunoglobulins and CD5+, CD19+, and CD20+ surface markers. Gene-rearrangement analysis with the Southern blot technique revealed multiple rearranged bands in each lane of restricted patient DNA after probing with both immunoglobulin heavy (J(H))- and light (J(kappa))-chain gene probes. Conclusions: Biclonal gammopathy in WM and biclonal B-cell proliferations as determined by gene-rearrangement studies are rare entities, and few evaluations of them are reported in the literature. To our knowledge, this case is the first one of biclonal WM to have been evaluated by serum protein immunofixation, immunohistologic staining, immunophenotyping by flow cytometry, and immunoglobulin gene-rearrangement analysis.