Triclonal gammopathy (IgAk, IgGk, and IgMk) in a patient with plasmacytoid lymphoma derived from a monoclonal origin

We report the case of a 64-year-old woman with plasma cytoid lymphoma of the ileum and gastric wall. Serum protein electrophoresis and immunoelectrophoresis showed a triclonal IgGkappa, IgAkappa, and IgMkappa gammopathy. Biopsy of the tumor revealed three different cell types, which were stained with antibodies specific for IgG, IgA, and IgM. However, DNA analysis of immunoglobulin gene rearrangements using J(H), C(mu), and Ckappa gene probes showed a monoclonal pattern. These results suggest that the three types of malignant cells producing different classes of immunoglobulins were derived from a single clone of B-cells that had undergone a "class switch".