Factors predicting transformation of asymptomatic IgM monoclonal gammopathy

We evaluated the risk of transformation of asymptomatic immunoglobulin (Ig) M monoclonal gammopathy (aIgM MG) into symptomatic lymphoproliferative disease in 287 patients all analyzed for bone marrow histopathology and immunophenotyping. This series included 201 patients with IgM MG of undetermined significance (IgM MGUS) and 86 with smoldering Waldenström's macroglobulinemia (sWM). After a median of 50 months (range, 12-322 months), 32 cases of aIgM-MG (11.1%) evolved into symptomatic malignant lymphoproliferative disease, as follows: symptomatic WM (n=26), non-Hodgkin lymphoma (n=6). The cumulative transformation percentage at 5 and 10 years was 8% and 19.5%, respectively. The parameters significantly correlated with evolution were, at univariate analysis, BM lymphoplasmacytic infiltration, high erythrocyte sedimentation rate, serum MC, serum IgM size, and serum IgA size. Among patients with aIgM-MG, those at high risk of evolution were patients with sWM, a distinct entity with serum IgM monoclonal protein≥3 g/dL and/or ≥10% bone marrow lymphoplasmacytic infiltration.