Diphtheria-toxin mediated abrogation of tissue-resident CD169+ macrophages in CD169-DTR mice, intratibially injected with myeloma cells from a syngeneic Vk*MYC mouse model, resulted in reduced dissemination of myeloma cells into the blood circulation and to the contralateral tibial bone. The gene discussed is SIGLEC1; the disease is plasma cell myeloma.