[Interpretation of minimal medullary plasmacytoses in monoclonal dysglobulinemias. Importance of the study of osteomedullary biopsies of semi-thin sections and immunologic marking].

A monoclonal gammopathy (M.G.) is usually associated with multiple myeloma or macroglobulinemia. Cases whose follow up have not demonstrated myeloma or lymphoma for several years are called "benign monoclonal gammopathies" (B.M.G.). Numerous criteria were suggested to distinguish multiple myeloma from B.M.G., chiefly an abnormal medullary plasmacytosis. But frequently it is only beyond 15 to 20 % that this plasmacytosis is considered as significative. Some authors have reported the peculiarities of these plasma cells immune labelling with rather conflicting results. We reviewed semi-thin sections of bone marrow biopsies with a low grade plasmacytosis (less than or equal to 10 %) by histological cytological and immunological methods in a group of 39 patients with a M.G. A diagnosis of multiple myeloma or of B.M.G. was made on the initial examination of these biopsies. The 24 cases of multiple myeloma were diagnosed using : --topographical criteria : inhomogenous sharing, nests of plasmocytes exclusively away from the periphery of vessels, --cytological criteria such as frequent cellular immaturity, nuclear immaturity in binucleated cells, bizarre shaped nuclei . . . --immunological criteria obtained by immunofluorescence method : strictly monoclonal labelling of plasma cells or "limit"-monoclonal labelling in 50 % of cases. The latter is less characteristic because of its presence in 25 % of B.M.G. In this prospective study, the initial diagnosis was maintained in 37 out of the 39 cases according to clinical and laboratory data. These results seem to demonstrate the practical value of the proposed criteria.