Biclonal gammopathy (IgG kappa and IgG lambda) in a patient with non-Hodgkin's lymphoma

We report a case of non-Hodgkin's malignant lymphoma with biclonal gammopathy (IgG kappa and IgG lambda) involving both serum and urine. Detailed immunologic studies of the tumor disclosed two morphologically indistinguishable clones of cells that were responsible for the production of the two monoclonal immunoglobulins. This, to our knowledge, is the first documented case of a biclonal gammopathy involving a single heavy-chain class with both kappa and lambda light chains in a non-Hodgkin's lymphoma. Lesions resembling lymphomas must not be assumed to be inflammatory simply because the cells express both kappa and lambda antigens.