ESTROGEN-RECEPTOR EXPRESSION IN NORMAL AN D TUMOROUS MAMMARY TISSUE IN DOGS AND HUMANS - A COMPARATIVE REVIEW OF THE LITERATURE

Oestrogen receptors (OR) have been found in epithelial cells of normal and tumourous mammary gland tissue of dogs and humans. The expression of OR is related both to the hormonal cycle and to age. Normal canine mammary tissue contains more OR than human breast tissue, especially during the luteal phase. The presence of OR in human mammary tumours i s associated with a better differentiation of the tumour cells and a l ower proliferation speed. In human medicine OR expression is used beca use of its prognostic value and for choosing a therapy. There are nume rous differences between dogs and humans regarding the expression of O R in normal and tumourous mammary tissue. Therefore the usefulness of the dog as an animal model for studying human breast cancer is questio nable.