Immunohistochemical detection of p53 and c-myc proteins in canine mammary tumours.

The objectives of this study were to detect by immunohistochemical means, nuclear accumulations of p53 and c-myc proteins in mammary tumours of dogs. Moderate or intense p53 protein nuclear labelling was shown by each of five osteosarcomas. In contrast, focal immunoreactivity was shown by three of five adenocarcinomas and two of three malignant myoepitheliomas. Six benign mixed tumours and three myoepitheliomas showed no detectable immunoreactivity. On the other hand, three patterns of c-myc protein nuclear reactivity were observed in these tumours. Osteosarcomas, adenocarcinomas, malignant myoepitheliomas and myoepitheliomas showed intense or moderate reactivity. In benign mixed tumours, the epithelial component showed moderate or intense reactivity, and the myoepithelial component showed focal or moderate reactivity. These results demonstrated that p53 protein was expressed only in the osteosarcomas, but that c-myc expression was detectable in both the epithelial and myoepithelial components.