Faculty Bibliography

A monoclonal paraprotein in the serum or urine raises the possibility of myeloma. However, in a significant proportion of individuals with serum paraproteins, particularly those with low levels of paraprotein, clinical and routine bone marrow evaluation is not diagnostic of an underlying neoplasm. The purpose of this study was to define the pathologic basis for monoclonal gammopathy in patients whose bone marrow biopsies showed no evidence of myeloma. We used immunofluorescence microscopy and flow cytometry of cell suspensions prepared from aspirated marrow, as well as immunohistochemistry of core biopsies, to perform immunopathologic evaluations of the bone marrow from 26 such patients. Eighteen patients with myeloma and seven without a serum paraprotein or evidence of myeloma were similarly studied. The data indicate that 17 of the 26 patients with monoclonal paraproteins whose routine bone marrow biopsies were normal or nondiagnostic had, in fact, a dispersed monotypic plasma cell population of concordant immunoglobulin heavy and light chain type in the bone marrow demonstrable by at least one of the three analytic methods. Among these, immunofluorescence microscopy of isolated bone marrow mononuclear cells was the most sensitive assay. Immunophenotypic evaluation of the bone marrow is useful for documenting and quantifying a monoclonal plasma cell population in patients with monoclonal gammopathy of undetermined significance

The presence of a monoclonal paraprotein in the serum or urine raises the possibility of myeloma or lymphoma/leukemia. Yet, in a significant proportion of individuals with serum paraproteins, particularly those with low levels of paraprotein, clinical and routine bone marrow evaluation is not diagnostic of an underlying neoplasm. The purpose of this study was to define the pathologic basis for macroglobulinemia in patients whose routine bone marrow biopsies were not diagnostic of a lymphoplasmacytic neoplasm. We used immunofluorescence microscopy and flow cytometry of cell suspensions prepared from aspirated marrow, as well as immunohistochemistry of core biopsies, to perform immunopathologic evaluations of the bone marrow from 16 such patients. Seven individuals without a monoclonal serum paraprotein, who were similarly studied, served as controls. Our data indicate that 13 of the 16 patients with monoclonal serum IgM paraproteins whose routine bone marrow biopsies were normal or showed nondiagnostic changes morphologically had a dispersed monotypic B lineage population of concordant immunoglobulin heavy and light chain type in the bone marrow. The immunophenotype of these cells spanned the range from mature B cell to plasmacytoid B cell to plasma cell. In four of these 13 patients a diagnosis of lymphoplasmacytic lymphoma could be made on the basis of greater than or equal to 20% monoclonal B lineage cells among bone marrow mononuclear cells