IgM plasmacytoma. Report of a case and review of the literature.

IgM paraproteinaemia is described in a patient with diffuse plasmacytoma involving the pleura, lymph nodes, and kidneys. Sixteen cases of pure plasmacellular tumor (diffuse or solitary plasmacytoma and plasmacellular leukaemia) associated with IgM paraproteinaemia have only been reported. These cases and experimental data indicate that neoplastic plasma cells can synthetize IgM as well as other immunoglobulins and that this particular M component is not associated solely with Waldenström's macroglobulinaemia.