Mammary cancer is the most frequently diagnosed neoplasia in women and non-spayed female dogs and is one of the leading causes of death in both species. Canines develop spontaneous mammary tumors that share a significant number of biological, clinical, pathological and molecular characteristics with human breast cancers. This review provides a detailed description of the histological, molecular and clinical aspects of mammary cancer in canines; it discusses risk factors and currently available diagnostic and treatment options, as well as remaining challenges and unanswered questions. The incidence of mammary tumors is highly variable and is impacted by biological, pathological, cultural and socioeconomic factors, including hormonal status, breed, advanced age, obesity and diet. Diagnosis is mainly based on histopathology, although several efforts have been made to establish a molecular classification of canine mammary tumors to widen the spectrum of treatment options, which today rely heavily on surgical removal of tumors. Lastly, standardization of clinical study protocols, development of canine-specific biological tools, establishment of adequate dog-specific disease biomarkers and identification of targets for the development of new therapies that could improve survival and have less adverse effects than chemotherapy are among the remaining challenges.

Cancer is one of the main causes of death in dogs and cats. What was once considered a death sentence is now a disease that can be treated and in most cases, it is possible to extend survival times with good quality of life. Antineoplastic treatment is usually a combination of multiple therapeutic modalities, in which surgery plays an important role for diagnosis and local control of the disease. Chemotherapy, and most recently immunotherapy, help in the systemic control of the remaining disease. Other modalities such as electrochemotherapy, radiotherapy and cryosurgery can also help in the management of cancer patients. In Mexico, oncology is still a novel medical specialty, but one in constant development.