Coexistence of nonsecreting and nonproducing light chain multiple myeloma

A 61-year-old female patient presented with osteolytic skeletal lesions. Open rib biopsy disclosed tumor tissue which consisted of two types of cells: massive infiltrates of poorly differentiated lymphoplasmacytic cells were surrounded by large deposits of differentiated plasma cells. Serum immunoglobulins were normal. No light chains could be found in the urine. An immunoperoxidase technique was employed to detect intracellular immunoglobulins. While the partially differentiated cells were negative, the plasma cells were stained strongly positive for kappa light chains.