Progesterone receptor expression and proliferative activity in uterine tumours of pet rabbits.

Endometrial adenocarcinoma is the most common uterine tumour of domestic rabbits. The present immunohistochemical study examined the expression of cytokeratin 19 (CK19), the progesterone receptor (PR), the proliferation-associated antigen Ki-67 and telomerase in normal rabbit uterine tissue and examples of endometrial hyperplasia, adenoma and adenocarcinoma. Tubulopapillary adenomas and adenocarcinomas were the most common histological subtypes in this series. Cytoplasmic expression of CK19 was recorded in two of three samples of normal endometrium and in one of three samples of endometrial hyperplasia, in all adenomas and five of six adenocarcinomas. PR was expressed within the nucleus of normal endometrial cells and in one of three samples of endometrial hyperplasia, each of four adenomas and in four of six adenocarcinomas. This finding suggests that PR expression is not directly involved in neoplastic transformation of the endometrium and that such expression is not a prognostic indicator. Nuclear labelling of telomerase activity was found in one of three normal uteri, all samples of endometrial hyperplasia, two of four adenomas, but none of the adenocarcinomas. The proliferation index as determined by Ki-67 expression was 9.7+/-2.75% (mean+/- standard-deviation (SD)) for normal endometrium, 11.29+/-2.5% for hyperplastic endometrium, 19.40+/-3.01% for benign tumours and 19.41+/-7.9% for malignant tumours. These findings may be interpreted to suggest that hormonal and anti-proliferative treatment may be more appropriate for the management of uterine carcinomas in rabbits than anti-telomerase treatment.