Differential diagnosis of Waldenstrom's macroglobulinemia from other low-grade B-cell lymphoproliferative disorders.

Waldenstrom's macroglobulinemia (WM) is a rare lymphoproliferative disorder (LPD) characterized by lymphoplasmacytic infiltration of the bone marrow (BM) and/or occasionally other tissues and by the presence of a serum monoclonal IgM. The disease belongs to the lymphoplasmacytic lymphoma (LPL) subtype. Whether WM is indeed a separate entity or is merely an IgM-secreting subtype of low-grade B-cell lymphoma is still controversial. In our series of 67 patients, WM has a long median overall survival of 110 months, and the male/female ratio is 1.2/1. Clinical features include a wide spectrum of manifestations, many of which may be common to other LPDs. Differential diagnosis is based on: (1) clinical and laboratory features (anemia, organomegaly, lymphadenopathy, IgM paraproteinemia), (2) cell morphology (lymphocytes, lymphoplasmacytes, few plasma cells), (3) histopathology of bone marrow or lymph node, (4) immunophenotype (CD5 expression and the intensity of CD5, CD20, and CD79b antigens may help in discrimination from other LPDs and atypical CLL), and (5) characteristic genetic features (present in other LPDs). Based on the former, diagnosis is usually easy. It may be harder in LPL cases not secreting IgM. We consider that WM should be, for the time being, handled as a separate entity. Further studies are necessary.