We described a rare case of multiple myeloma in a 60-year-old man, in whom relapse limited to the irradiated area in the left lobe of the liver developed following radiotherapy for lesions in 11th and 12th thoracic spines. Immunohistochemical analysis revealed expression of hepatocyte growth factor (HGF) and hepatocyte growth factor receptor (c-Met) in the hepatocytes in the irradiated area of the liver. We speculate that the malignant plasma cells might have proliferated in response to local increase of HGF production in the irradiated liver. The role of HGF in the extraosseous spread of multiple myeloma and also under the experimental condition of hepatic transplantation is discussed.
