A significant association was found between P-cadherin expression and histological grade of carcinomas, as previously reported by other authors in human breast cancer [11,21,23,24,26,27,62,66-68] and canine mammary tumours [16,56], suggesting that this molecule may be regarded as a prognostic indicator of aggressiveness in feline mammary carcinomas. The gene discussed is CDH3; the disease is carcinoma.