The rounded lucency seen here in the upper shaft of the femur is a plasmacytoma, a collection of plasma cells. In another case below, the lytic distal femoral lesion is more subtle. Since these patients had other lesions, this is not a solitary plasmacytoma, but multiple myeloma. His total serum immunoglobulin level was greatly increased, with an IgG "spike" seen on serum protein electrophoresis and bands of IgG and kappa on immunoelectrophoresis of serum.