4.1. Animals and Sampling

In the present study, a total of 30 bitches referred to the Teaching Veterinary Hospital (Fundació Hospital Clínic Veterinari) at Universitat Autònoma de Barcelona (UAB, Catalonia, Spain) and diagnosed with mammary tumours were included. Patients were aged between 6 and 13 years (mean age: 10.3 years) and belonged to different dog breeds. All females were subjected to surgery to remove the mammary tumours. Once removed, the masses were fixed with 10% paraformaldehyde (Sigma-Aldrich, Barcelona, Spain) and submitted to the laboratory for tumour typification through hematoxylin/eosin histologic evaluation. Samples were further embedded in paraffin and four to five 10 μm sections from each paraffined tumour were obtained for RNA extraction.

A total of 58 mammary samples were submitted for histology purposes. In addition, healthy mammary tissue from 3 bitches was also included as a control group. Specimens were obtained according to the guidelines of the Ethical Committee of Animal Care and Research of the UAB (protocol CEEAH number 1127, 20 March 2012).