4.1. Tissue Samples

The samples utilized in this work were retrospectively retrieved from the Department of Pathology, University of Veterinary Medicine Hannover, Hannover, Germany, between the years 1993 and 2000. The mammary specimens were fixed in 10% neutral buffered formalin as routinely performed and embedded in paraffin wax. The blocks were stored in the archive at room temperature. A total number of 170 samples were selected for the analysis.

The samples were obtained from patients which had undergone surgery in the Small Animal Clinic, University of Veterinary Medicine Hannover, Hannover, Germany, between 2003 and 2011 (identification number: 96A697; 19 January 2005), as well as from patients from the Clinic of Small Animals, Institute of Veterinary Medicine, Georg-August-University Göttingen, Göttingen, Germany, from 2013 and 2014. All utilized tissue samples were removed with consent of the owner. The specimens were frozen in liquid nitrogen directly after surgical removal and maintained at −80 °C until RNA isolation. A total number of 111 samples were selected for the analysis.