Monoclonal IgM-secreting neoplasms. Clinical and morphologic heterogeneity

Two patients with monoclonal IgM-secreting neoplasms are presented. Though both patients could be diagnosed as Waldenström's macroglobulinemia, the clinicopathologic features were quite contrastive. Most neoplastic cells in Case 1 showed lymphocytic morphology with rather leukemic process, while those in Case 2 were highly polymorphic with solid proliferation. The clinical and morphologic heterogeneity in these cases and cases in the literature is discussed, and the possible requirement to establish a system for the subclassification of IgM-secreting neoplasms is insisted.