Clinical, epidemiological, and histopathological aspects of breast cancer in female dogs at Federal Rural University of Rio de Janeiro Veterinary Hospital

This study aimed to evaluate the clinical, epidemiological, and histopathological aspects of canine breast tumors at the Federal Rural University of Rio de Janeiro Veterinary Hospital (VH-UFRRJ) between April 2017 and October 2018. The study included 137 female canine dogs with mammary neoplasia who underwent a mastectomy. The animals were evaluated using a standard form that guided anamnesis and physical examination to assess the tumor’s epidemiology, development, evolution, treatment choice, and disease prognosis. Furthermore, laboratory and imaging tests were performed on the animals to search for changes that suggested metastasis. The average age of the female dogs was 10 years, and mixed-breed dogs (33%) were the most affected, followed by poodles (21%). The inguinal (79%) and caudal abdominal (64%) breasts were the most affected. Approximately 26% of the animals were castrated, 32% had already reproduced throughout their lives, 30% had pseudocyesis, and only 8% used contraceptive methods. The majority were classified as stage I (33%) and stage III (39%) according to the Tumor-Node-Metastasis (TNM) Classification System of Malignant Tumors. In 95 female dogs, 191 nodules were histopathologically evaluated, and 62% of these animals had at least one malignant tumor. Statistically, there was a direct association between tumor size and malignancy. However, other associations, such as age at diagnosis and the degree of malignancy, were not confirmed. Therefore, it can be concluded that tumor size is an important prognostic factor, with tumors >3 cm having an approximately 70% chance of being malignant.