Expression of Myoepithelial Markers p63 and 14-3-3 in Canine Mammary Tumours

p63, a p53 homologue nuclear transcription factor was expressed in basal cells of multilayered epithelia and myoepithelial cells of the breast. 14-3-3 was a putative tumour suppressor gene, transactivated by p53 in response to DNA damage and immunohistochemically demonstrated that 14-3-3 was consistently expressed in the cytoplasmic compartment and occasionally in the nuclei of myoepithelial cells. In the present study, p63 immunoreactivity was restricted to nucleus of myoepithelial cells. Eighty per cent of tumours showed immunopositivity. Mild to moderate staining was noticed. The intensity of staining in carcinomas / carcinosarcomas were mild in 40 per cent, moderate in 25 per cent and intense in 15 per cent. p63 expression was found in 80 per cent of the canine mammary tumours evaluated. Malignant mixed tumours showed 40-80 per cent immunoreactivity. It was 85-95 per cent in spindle cell carcinoma and 70-90 per cent in squamous cell carcinoma. 80-90 per cent p63 immunopositivity was noticed in squamous cell carcinoma. In cystadenoma, no immunoreactivity was observed. 14-3-3 immunoreactivity was observed both in the nuclear and cytoplasmic components of myoepithelial cells. 14-3-3σ immunoreactivity was observed in 95 per cent of the tumours evaluated and immunoreactivity was noticed both in the cytoplasmic and nuclear components. Benign tumours showed 5% expression and malignant mixed tumours showed 25 80 per cent 143-3σ immunoreactivity. Squamous cell carcinoma showed 80 per cent immunoreactivity.