Immunohistochemical evaluation of ovarian hormonal receptors in canine mammary tumors

Background: In female dogs, ovarian hormones have a crucial role in the pathogenesis of mammary tumors. Ovarian hormones interact with nuclear receptors, estrogen receptor α (ERα) and β (ERβ), progesteron receptor (PR) and andro- gen receptor (AR) respectively. The aim of this study was to verify the existence of correlations between biological be- haviour and immunohistochemical expression of estrogen receptor α (ERα) and β (ERβ), progesterone receptor (PR) and androgen receptor (AR) in canine mammary tumors. A total of sixty-four tumors were examined. Results: The ex- pression of every receptor was higher in normal tissue and benign tumors than in malignant neoplasm. Among malig- nancies, the lowest levels of every receptor were detected in high grade carcinomas (p < 0.01). Lower levels of ERα and PR were associated with regional (p < 0.01) and/or distant (p < 0.05) metastasis. A lower expression of ERβ was found in carcinomas with nodal positive status (p < 0.05). High level of AR seemed weakly associated with the development of distant metastasis (p > 0.05). Conclusions: The expression of ERα and/or PR showed the positive prognostic value for the Spearman’s rank test (p < 0.01). ERβ also displayed a positive prognostic significance (p < 0.05). The levels of AR were inversely correlated only with grading of a slight positive correlation with metastatic power of carcinoma (p > 0.05). In human breast carcinoma, AR seems to be involved in metastatic development by up-regulation of metallopro- tease of matrix (MMP). Therefore, evaluating the correlation among the presence of AR, expression of MMP and ap- pearance of distant metastasis also in canine mammary tumors could be very interesting.