Feline endometrial adenocarcinomas are uncommon malignant neoplasms that have to date been poorly characterized. The present immunohistochemical study describes the expression of the pancytokeratins AE1 and AE3, cytokeratin-14, vimentin, alpha-actin, cyclo-oxygenase-2, E-cadherin, beta-catenin, the progesterone receptor, the oestrogen receptor and caveolin-1 within normal feline uterine tissue and tissue from six cats with endometrial adenocarcinoma. Synthesis of cyclo-oxygenase-2 and reduced expression of progesterone receptors may be involved in the neoplastic transformation of feline endometrium. The loss of cellular adhesion that occurs within these tumours does not require down-regulation of E-cadherin expression and nuclear translocation of beta-catenin is not a feature of these neoplasms.