A case of multiple myeloma which developed into multiple extramedullary involvement in the terminal stage.

A 69-year-old man with a diagnosis of multiple IgG class myeloma received combination chemotherapy. He achieved a partial response with an undetected M spike. However, he demonstrated new lytic bone lesions and multiple extramedullary involvement 10 months after the initial presentation. Polymerase chain reaction (PCR) analysis using a framework 3 (Fr3) V-region primer clarified a discrete band in the extramedullary tumor, while it yielded 4 bands including the same size as the extramedullary tumor produced in the bone marrow sample obtained before the chemotherapy. These findings suggest that a resistant and non-secretory clone was selected by the combination chemotherapy.