A case of primary lung cancer with synchronous costal plasmacytoma

Background. Multiple myeloma is a malignancy that derives from plasma cells. Some are diagnosed with a solitary plasmacytoma developing on spines, bones of the extremities or ribs, but few cases are reported that have multiple myeloma combined with primary lung cancer. We encountered a case of primary lung cancer with a solitary rib tumor, which was diagnosed as plasmacytoma. Case. A 73-year-old man found to have an asymptomatic tumor on the right 5th rib. This abnormal lesion was not pointed out before. Chest CT and PETCT showed a 15 mm sized tumor with spiculation and pleural indentation in the apex of the right lung (¹⁸F-FDG accumulation with the SUVmax of 7.93), and a 6 cm sized expansile tumor in the right 5th rib (¹⁸F-FDG accumulation with the SUVmax of 8.16). On operation, core needle biopsy was performed for these two tumors. Intraoperative rapid diagnosis was performed and we found the lung tumor was an adenocarcinoma, and the costal tumor was suspected to be a plasmacytoma. Subsequently, a right upper lobectomy ND2a-1 was performed by completely video-assisted surgery. The patient was given a diagnosis of primary lung adenocarcinoma (pT1aN0M0 stage IA) and a plasmacytoma of the right 5th rib. General examination was followed after the diagnosis, and a monoclonal gammopathy (IgG λ type) and an increase of plasma cells in the bone marrow were found, and symptomatic multiple myeloma was finally diagnosed. Conclusion. We report a rare case of primary lung cancer combined with symptomatic multiple myeloma which developed a single plasmacytoma on the rib.