Steroid receptors and proliferative activity in non-neoplastic and neoplastic endometria

In the glands of cyclic endometria, proliferative activity (PA), as revealed by expression of the Ki-67 antigen, is highest in the proliferative phase (P) and early secretory phase (S1). The PA decreases in the middle secretory phase (S2). In the stroma the PA is low during the whole cycle. In P and S1, the oestrogen receptor (ER) and the progesterone receptor (PR) are strongly expressed in glands and stroma. The number of positive cells and the staining intensity decreases in S2, particularly in the glands. In atrophic endometria, fibro-glandular polyps and in endometria with arrested secretion the PA is low in both glands and stroma. ER and PR can be detected in glands and stroma. The PA in atypical hyperplasias is only slightly higher than in cyclic endometria and endometria with simple hyperplasia. The ER and PR levels are comparable to those in proliferative endometria. The PA of endometrial adenocarcinomas is positively and the ER and PR negatively correlated with the degree of de-differentiation. No ER-negative carcinoma displays the PR. Immunohistologically, non-neoplastic receptor positive tissue can be seen in many ER- and PR-negative carcinomas. These structures may falsify the biochemical receptor analysis.