lymphoplasmacytic lymphoma (LPL) includes most cases of Waldenstroms macroglobulinemia and consists of a diffuse proliferation of small lymphocytes, plasmacytoid lymphocytes and plasma cells; the typical histologic features of small lymphocytic lymphoma, mantle cell lymphoma and marginal zone lymphoma must be absent

B-cell antigens are positive; whereas CD5 and, usually, CD23 test negative; the cells express surface and cytoplasmic IgM and are IgD-. CD10 is negative, whereas a proportion of cases have faint CD25 and CD11c expression; the postulated normal counterpart is a B-lymphocyte differentiating into an IgM-secreting plasma cell

the number of cases studied is small and the interpretation of data must take into account possible variability of histologic classification