Significance of M-components in Plasma Cell Myeloma and Related Disorders

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Some clinical and immunochemical findings are presented in 203 patients with M-components. These include 148 patients belonging to primary-malignant group - myeloma, primary macroglobulinemia, and potentially malignant type-, 9 patients with malignant lymphomas and various types of M-components, and 46 patients with benign monoclonal gammopathy. When M-component was present, the following findings seemed to support the diagnosis of myeloma: (1) the concentration of IgG-M-components over 2.0g/100ml or that of IgA-M-components over 1.0g/100ml, (2) presence of Bence-Jones proteins in serum or urine, (3) BBC below 3million/mm³, (4) serum albumin below 3.0g/100ml, (5) plasma cells over 10% in the bone marrow, and (6) presence of plasma cells with marked cytological abnormalities. Since there was a considerable overlap between myeloma and benign monoclonal gammopathy, these findings should be evaluated as a whole, not separately, together with other clinical features, and radiological and histological findings. There was no overlap in the concentration of monoclonal IgM between primary and secondary macroglobulinemia, but the number of cases is too small to draw definitive conclusions. The term `potentially malignant type' has been proposed by the author in order to contribute to the study on the pathogenesis of myeloma or related disorders and the development of tumors in general. Since this condition cannot be regarded as wholly benign, patients should be examined repeatedly for a long period. The mechanisms of occurrence of M-components in malignant lymphomas, its relationship to prognosis, and electrophoretic mobility and immunologic types of M-components are discussed.