Expression pattern of c-erbB2 and estrogen receptor-α in spontaneous canine mammary tumours

C-erbB2 and ERα are implicated in carcinogenesis of mammary gland and reproductive tumours. In the present study, expression pattern of c-erbB2 and ERα was investigated in different histological subtypes of spontaneous canine mammary tumour samples by immunohistochemistry (n=103). The pattern of expression of c-erbB2 and ERα was correlated semi-quantitatively with respect to histological subtypes. C-erbB2 overexpression was seen in both membrane and cytoplasm of transformed cells. 33.9% of tumours overexpressed c-erbB2 and its expression was exclusively limited to malignant epithelial tumours. C-erbB2 expression was significantly higher in solid carcinomas, however there was no significant difference between other histological subtypes. ERα expression was found in the nucleus of normal and neoplastic epithelial and myoepithelial cells. 79.6% of tumours reacted positively for ERα. Simple adenoma had significantly higher levels of ERα expression compared to malignant tumours (P=0.05). Among malignant tumours solid carcinomas and carcinosarcoma had significantly lower ERα expression. However, there was no significant difference in ERα expression between tubular adenocarcinomal papillary adenocarcinoma and malignant mixed tumours. Further, c-erbB2 overexpression was associated either with ER± negativity or its lower expression (P = 0.01). These findings suggest that overexpression of c-erbB2 and loss of ERα expression associated with malignant transformation and higher degree of malignancy.