Role of body condition score and adiponectin expression in the progression of canine mammary carcinomas

Abstract

Obesity has been identified as a risk factor for developing breast cancer in post-menopausal period in humans and has been suspected to be associated with a worse prognosis also in the bitch. The aims of this study were to investigate the association between body condition score (BCS) and the prognosis of canine mammary carcinomas (CMCs) and the relationships between adiponectin expression and tumour behaviour. Seventy-three bitches with tubular, tubulopapillary, solid or complex carcinomas were included in the present study. For each dog, evaluation of BCS was conducted using a nine-point BCS system and the study population was divided into normal weight (4-5/9 points; n = 42), overweight (6-7/9 points; n = 19) and obese (8-9/9 points; n = 12). Type of diet (commercial, homemade or mixed) was recorded. After surgical excision, histological type, tumour size and nodal status were assessed and adiponectin expression was determined and quantified by immunohistochemistry and morphometric analysis. CMC histotype was not correlated with BCS, while a positive correlation between BCS and histological grade (p < .01) was observed. Overweight and obese bitches combined showed a shorter cancer-specific survival than normal weighted bitches (p < .01). Bitches fed with a homemade diet had a higher BCS than dogs fed with a commercial one, although no relationship was observed between diet and cancer-specific survival. Thirty-six CMCs scored positive for adiponectin expression (49%), but no correlation was found between the hormone expression and either CMC characteristics or prognosis. In conclusion, a higher BCS seems to be related with a higher prevalence of more aggressive CMCs and negatively affects the survival time in bitches with these mammary tumours.

Keywords: adiponectin; body condition score; canine mammary tumour; immunohistochemistry; obesity; cancer-specific survival.

Figure 1

Canine mammary tissues. Immunohistochemical staining of adiponectin (Horseradish peroxidase and haematoxylin counterstain; Bar =50 µm). (a) Adiponectin‐negative labelling in normal mammary tissue. (b) Weak immunostaining in dysplatic cells in a lobular hyperplasia adjacent to a malignant mammary neoplasm. (c) Strong staining in more than 75% of neoplastic cells in an adiponectin‐positive tubular simple carcinoma. (d) Strong staining in most neoplastic cells and in myoepithelial cells in an adiponectin‐positive complex mammary carcinoma

Figure 2

Cancer‐specific survival curves (a) for the group of 73 bitches bearing mammary carcinomas subdivided depending on BCS (normal: blue line, overweight and obese: green line; p < .01)

Figure 3

Cancer‐specific survival curve (a) for the group of 73 bitches bearing mammary carcinomas subdivided depending on the type of diet (homemade diet: blue line, commercial diet: green line and mixed diet: yellow line; p > .05)