A 53-year-old woman was admitted to this institution with chest pain and dyspnea. Chest roentgenogram showed pleural effusion and multiple tumor shadows, bilaterally which represented extrapleural signs. Numerous atypical plasma cells were found in the pleural effusion. Bone marrow biopsy showed atypical plasma cells. Immunoelectrophoresis revealed monoclonal Bence-Jones protein-lambda in serum and urine. Myeloma was subsequently diagnosed and chemotherapy was started. Multiple myeloma is a plasmacytoma, and myeloma cells proliferate in the bone marrow. The incidence of myeloma associated with malignant pleural effusion is rare with only 33 cases previously reported in Japan, to the best of our knowledge.
