[A case of solitary plasmacytoma of the chest wall].

A 58-year-old man with a solitary plasmacytoma of the chest wall is reported. He was admitted because of a painless tumor on the right lateral chest wall. The chest CT scan showed a chest wall tumor surrounding the 7th and 8th ribs without rib destruction. A transcutaneous needle biopsy of the tumor with a Sure-Cut-Needle revealed a plasmacytoma. The bone marrow biopsy findings were normal. Under a diagnosis of solitary plasmacytoma, the chest wall tumor was resected. The tumor was an extramedullary plasmacytoma. Southern blot analysis of the immunoglobulin light chain gene of the tumor cells detected a rearrangement of genes in the lambda chain, while no rearrangements of immunoglobulin genes were detected in the bone marrow specimen. Seven months later another solitary plasmacytoma was found at the left radius, and was resected. Southern blot analysis of the immunoglobulin light chain gene was useful in the differential diagnosis from systemic myeloma and in determining the monoclonality of the tumor.