In this study, we have analyzed the phenotypic and genomic abnormalities present in theMef−/−Rad50s/s mice, establishing a novel and transplantablemouse model of multiple myeloma and plasma cell neoplasms which mimics the human diseaseand is not attributed to the activation of a specific oncogene or inactivation of aspecific tumor suppressor gene (other than Mef). Here, ELF4 is linked to plasma cell myeloma.