Obesity and canine mammary tumors: correlations between BCS, adiponectin expression, clinical pathological features and overall survival

Obesity was identified as a risk factor for developing breast cancer in the women postmenopausal period and is also associated with a higher risk of lymph node metastasis (1). Obesity is associated with a worse prognosis also in the bitch (2). The aims of this study were to investigate: the correlation between body condition score (BCS) and some prognostic factors (overall survival, histology and grade of mammary gland tumours), the influence of diet on the BCS and the correlations between adiponectin expression, tumor histological type, histological grade and overall survival at 730 days after mastectomy. Seventy three bitches presenting with simple, complex or solid carcinomas of the mammary glands were included in the present study. For each dog, an accurate weight assessment was conducted using a nine-point BCS system and the study population was divided into three groups: normal weight (4-5/9)(n=42), overweight (6-7/9)(n=19) and obese (8-9/9)(n=12). Type of diet and eating habits were recorded. After surgical excision, histological type, tumor size, and nodal status were determined according to WHO criteria (3). Immunohistochemistry was performed for the evaluation of adiponectin expression using a mouse monoclonal anti adiponectin primary antibody (ab22554) and streptavidin peroxidase system as detection method. Staining intensity and staining distribution were both assessed with a specific 4 point scoring system. If the sum of scores was greater than 2, the sample was considered positive; otherwise, it was negative. No differences were found between BCS and histological types, while BCS was correlated to a worse histological grade (P<0.01). Overweight and obese bitches showed a shorter overall survival than normal weight bitches. Bitches fed with a homemade diet had a higher BCS than dogs fed with a commercial one, and it was observed a correlation between diet and overall survival of dogs after the mastectomy. A homemade diet seems to be generally worse probably because it is often unbalanced and not correctly integrated, predisposing to obesity and consequently increasing the risk of developing mammary gland carcinoma. In neoplastic mammary gland tissue, the adiponectin expression was positive for 36 samples (49%) and negative for 37 (51%). No statistical correlation was found between adiponectin expression, histological type and histological grade and, therefore, it can’t be considered a positive prognostic factor for mammary gland carcinoma in dogs. In conclusion, an higher BCS affects the survival time and the histological grade of breast canine mammary carcinoma.