Histological and immunohistochemical study of the canine prostate.: Is the dog a valuable model for the study of the precursor of the human prostate cancer?

Introduction : In this study, prostate cancer of the dog and its precursor, the prostatic intraepithelial neoplasia (PIN), are investigated to determine if the dog could be a valuable model of the human prostate cancer. Materials and methods : 22 prostates from dogs over 7 years old that had no clinical evidence of prostatic disease were evaluated. The description of the normal epithelium and the prevalence of both PIN and cancer were determined by systematic evaluation of hematoxylin/eosin stained serial tissue sections. Immunohistochemistry (epitope Ki 67 and cytokeratin) was performed. Results : The normal epithelium of the canine prostate shows some differences with its human counterpart. The nucleus is vesicular and is similar in this way to the nucleus of the epithelium of human seminal vesicles. The basal cell layer was not seen with hematoxylin/eosin staining. Immunohistochemistry allowed to discern the basal cell layer in atrophic lesions but rarely and with disruption in normal epithelium. In our study, there were no cases with cancer or high grade PIN. Four foci, where low grade PIN was suspected with hematoxylin/eosin staining, were in fact atrophic lesions after immunohistochemistry. Discussion : The prevalence of canine prostate cancer and of its precursor is absent in our series, whereas prostate cancer occurs frequently in humans. It seems that the dog is not a valuable model for study of spontaneous prostate cancer.