Mammary tumours in 214 dogs were evaluated at the Department of Surgery and Orthopaedics, Veterinary and Pharmaceutical University Brno, between 1997 and 2001. Lesions of the mammary gland were classified as dysplasia/hyperplasia, benign and malignant tumours in 19, 61 and 134 patients, respectively. When there were different lesions of the mammary gland in one individual, the patient was classified according to the most malignant one. The above-mentioned patients were compared to the population of 17 053 dogs treated during the same period to determine age and breed predisposition. Considering the lesions of the mammary gland, the highest relative risk of dysplasia/hyperplasia, benign tumours and malignant tumours was at the age of 8, 10 and 13 years, respectively. Our results thus confirm the previous studies stating the highest incidence after 10 years of age. Poodles, English Cocker Spaniels and Dachshunds had a statistically significant relative risk developing benign and malignant tumours of the mammary gland (χ2-test, p < 0.01), confirming conclusions of previous studies concerning these breeds. We did not, however, prove higher relative risk in Irish Setters, Labrador Retrievers and Boxers.
Zatloukal, J., Lorenzová, J., Tichý, F., Nečas, A., Kecová, H., & Kohout, P. (2005). Breed and age as risk factors for canine mammary tumours. Acta Veterinaria Brno, 74(1), 103–109. https://doi.org/10.2754/avb200574010103