Factors influencing the occurrence of mammary gland tumours in dogs

Abstract

During the study period, out of 24,473 clinical cases, 180 (0.74%) dogs showed tumours, of which 92 (51.11%) were skin tumours and 88 (48.89%) were mammary tumours. The incidence of mammary tumours in relation to canine attendance to the hospital was 0. 36%. The mean age of mammary tumour occurrence was 9.2 years with an age range of 2–16 years. Mammary tumours were recorded in 96.67% females and 3.33% male dogs. The highest incidence occurred in purebreeds 66 (73.33%) followed by non-descript 22 (24.44%) and cross-bred dogs 2 (2.22%). Among the pure breeds, Spitz 21 (31.82%), Doberman 11 (16.67%) and German Shepherd 11 (16.67%) were commonly affected. Out of 87 female dogs, 90.80% were intact and 37.93% dogs were whelped at least once. The number of intact animals was slightly higher and animals that have whelped were lower. Six were spayed before breeding and two were spayed after one whelping, which had a protective effect on the occurrence of mammary tumours. The highest incidence occurred in the posterior glands (n=99) including inguinal glands 52 (40.00%) and caudal abdominal glands 47 (36.15%). Of the 90 cases, 10 (11.11%) showed pulmonary metastases on radiograph and one dog had metastases in the heart and the lung on necropsy. The factors influencing the occurrence of mammary tumours in dogs should be considered in the evolution of these tumours and for a better prognosis and treatment.