Animal models are important tools to investigate the pathogenesis and develop treatment strategies for bone metastases as they occur in humans. However, there are few spontaneous models of bone metastasis despite the fact that rodents (rats and mice) and other animals, such as dogs and cats, often spontaneously develop cancer. Therefore, most experimental models of bone metastasis in rodents require injection or implantation of neoplastic cells into orthotopic locations, bones, or the left ventricle of the heart.