The presence of HER-2/neu (c-erbB-2) oncoprotein, oestrogen-alpha. receptor (ER), and progesterone receptor (PR) in hyperplastic endometrial polyps (EPs) of two cats with cystic endometrial hyerplasia-pyometra (CEH-P) complex was investigated. Immunohistochemistry assay for ER, PR and c-erbB-2 oncoprotein in the glandular and stromal tissue of the Ell's was performed. ER and c-erbB-2 immunoreactivity,vas observed in the glandular epithelium of the EPs whereas PR immunoreactivity was detected only in the stromal fibroblasts. The c-erbB-2 oncoprotein may play a role with the ER in the pathogenesis of the hyperplastic EPs, although the role of this oncoprotein in the pathogenesis of EPs has yet to be determined. (C) 2009 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.