Lymphoid Neoplasms Associated With IgM Paraprotein

Abstract

We identified 382 consecutive patients with lymphoid neoplasms associated with serum monoclonal IgM paraprotein and classified each neoplasm according to World Health Organization criteria. Lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) was most common, 225 cases (median serum IgM level, 2.2 g/dL; range, 0.2-10.9 g/dL). For 157 cases, classification and median (and range in g/dL) IgM levels were as follows: chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; n = 77), 0.9 (0.1-2.1); marginal zone lymphoma (n = 27), 0.5 (0.1-2.4); follicular lymphoma (n = 18), 0.4 (0.1-1.6); mantle cell lymphoma (n = 11), 0.4 (0.2-1.3); diffuse large B-cell lymphoma (DLBCL; n = 7), 0.5 (0.2-1.0); DLBCL associated with low-grade lymphoma (n = 5), 0.9 (0.4-3.0); angioimmunoblastic T-cell lymphoma (n = 4), 0.8 (0.8); and CD5+CD23- low-grade B-cell lymphoma, unclassified (n = 8), 0.5 (0.3-2.9). The results show IgM paraproteinemia was associated most commonly with LPL/WM (58.9%), followed by CLL/SLL (20.2%). Although serum IgM levels greater than 3 g/dL were restricted to patients with LPL/WM, most patients with LPL/WM had paraprotein levels less than 3 g/dL. Thus, serum IgM paraprotein level is not a reliable discriminator in differential diagnosis.