[A case of extramedullary plasmacytoma of the lung associated with nodular deposit of amyloid].

A 63-year-old man underwent left upper lobectomy because of a 35-mm tumor in the lingula. Microscopic findings showed that the tumor was composed of a proliferation of plasma cells, and that in some areas eosinophilic amorphous material had been deposited between the tumor cells. By immunoperoxidase staining, the tumor cells were positive for IgG and kappa chain, but they were negative for lambda chain. In addition to the tumor in the lingula, another nodule was found in the left lower lobe and was resected at thoracotomy. The nodule was composed of diffuse eosinophilic amorphous material, which was found to be amyloid after Congo red staining and observation in polarized light. In and around the nodule, a few plasma cells were noted and these cells were also positive for IgG and kappa chain, but negative for lambda chain immunoperoxidase staining. In serum taken from the patient before surgery, M-protein was not detected by immuno electrophoresis but polyclonal hypergammaglobulinemia was noted, and it continued after the thoractomy. Bone marrow examination and a bone scintigram revealed no abnormality. In this case, a pulmonary plasmacytma co-existed with nodular pulmonary amyloidosis. We could not determine which lesion developed first, but the results of the immunoperoxidase staining of plasma cells in both lesions indicate that the origin of the plasmacytoma was probably the same as that of the nodular amyloid.