The need for reliable prognostic markers and promising therapeutic approaches to treat feline mammary carcinomas, has led to an intensive research aiming to accomplish a molecular characterization of feline mammary tumours, that reflects their biological behaviour, similar to what has been previously performed in human breast cancer. The aim of this study is to characterize, by immunohistochemistry, the molecular markers of normal mammary gland, hyperplastic/dysplastic mammary lesions, and benign and malignant feline mammary tumours, applying phenotypical molecular markers (AE1/AE3, vimentin, p63), hormonal receptor status (estrogen receptor (ER), progesterone receptor (PR)) and markers of proliferative activity (Ki-67 index) as well as the classical cadherins P and E’s expression. In feline mammary carcinomas there was an overexpression of vimentin and p63, a higher proliferation index and a reduction in estrogen receptor expression, when compared with benign tumours. Carcinomas that were simultaneously P-cadherin-positive, vimentin-positive and estrogen-negative were associated with a higher histological grade. Moreover, P-cadherin and vimentin-positive tumours were also associated with the presence of neoplastic emboli, presenting a threefold likelihood of intravascular dissemination when compared with tumors in which the expression of these markers was absent. P-cadherin, vimentin and ER expression seem to be relevant molecular markers in feline mammary carcinomas associated with a more aggressive behaviour.
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