Abstract
In both humans and companion animals, cancer is one of the leading causes of death worldwide. Given the increasing incidence in humans and dogs, there is an urgent need to find or improve strategies for diagnosis, treatment and prognosis. Hence, the importance of having very similar study models. Both canine and feline models have advantages over their murine counterparts in the study of breast cancer and cancer in general. Among other things, at the molecular and genetic levels, in terms of risk factors, spontaneous disease onset and tumour heterogeneity, domestic animals share greater similarities with the human species than the murine model. In addition, they share environmental and socioeconomic factors. Another advantage is their similar response to chemotherapy treatment, and rapid imaging results can be obtained with the same screening techniques used in humans. Finally, this chapter discusses the main features that make the canine and feline model the main source for the study of breast cancer in vitro and in vivo.