The distribution of oestrogen receptors in normal, hyperplastic and neoplastic canine prostate, as demonstrated immunohistochemically.

The role of oestrogens and their receptors (ERs) in prostatic growth and differentiation and in the progression of prostatic carcinoma has been well investigated in human medicine. In dogs, however, available reports on the expression of ERs in normal, hyperplastic or neoplastic prostates are few and controversial, or completely lacking. Three normal, three hyperplastic and nine neoplastic canine prostates were examined histologically, and immunohistochemically with a polyclonal antibody directed against human ERs. Evaluation of the percentage of immunolabelled cells was performed by digital image analysis. The study showed that ERs were expressed in the nuclei of epithelial and stromal cells in normal, hyperplastic and neoplastic prostates. All nuclei in normal and hyperplastic prostates were strongly and homogeneously immunolabelled by the antibody used. However, the percentages of immunolabelled nuclei in the nine prostatic carcinomas were greatly reduced, ranging from 36.34% to 66.73%. The severe loss of ER expression in canine prostatic carcinomas may account for the relative lack of differentiation of these tumours in the dog.