Immunohistochemical Expression of E-Cadherin and β-Catenin in Feline Mammary Tumours.

E-cadherin and β-catenin have been studied in carcinogenesis and tumour progression and reduced membrane expression of these molecules in canine mammary tumours has been associated with a poor prognosis. The present study investigated immunohistochemically the expression of E-cadherin and β-catenin in 53 mammary tumours and 48 hyperplastic or dysplastic lesions from 57 queens. E-cadherin and β-catenin expression was membranous in all samples and there was a significant decrease in expression in malignant tumours and metastases. Cytoplasmic expression of both markers was inversely correlated to the membrane localization. β-catenin nuclear labelling was detected in one lymph node metastasis (60% positive cells) and in the basal/myoepithelial cells of 6/7 ductal tumours. No correlation with survival was found for either marker. These results confirm the role of these proteins in maintaining tissue architecture and in inhibiting cell invasiveness and potentially indicate the oncogenic potential of the Wnt/β-catenin transduction pathway in feline mammary tumours. In addition, specific independent expression of β-catenin in the nuclei of basal/myoepithelial cells might suggest that this molecule is involved in regulation of the mammary stem/pluripotent cell component. Further studies should include more cases of benign mammary neoplasia and further investigate β-catenin nuclear expression in ductal tumours.