[A case of extramedullary plasmacytoma of the lung diagnosed by video-assisted thoracic surgery].

A 69-year-old man who had had a history of abnormal chest radiograph was admitted. Chest computed tomography showed an 18 x 18 mm apparently-circumscribed mass in the right posterior-basal segment. We performed right lower lobe wedge resection via video-assisted thoracic surgery to establish a definitive diagnosis. The mass was an apparently-circumscribed, gray and solid tumor, the microscopic findings of which included diffuse proliferation of plasma cells with an abnormal profile. Immunohistochemical staining revealed IgG-kappa light chain monoclonality. Absence of M protein in the serum and urine was confirmed. Bone-marrow puncture and positron-emission tomography revealed normal findings. Thus a diagnosis of extramedullary plasmacytoma (EMP) of the lung was made. We report trends of the immunoglobulin isotype of EMP in Japan. Since it has been reported that some of the cases in EMP progress to multiple myeloma (MM), careful observation and follow-up is needed hereafter. In the present case, no recurrence or progress to MM was observed within the first year after surgery.