The oestrogen receptor (ER) in normal and abnormal uterine tissue.

Glandular epithelium and stroma of the endometrium show typical behavioural patterns in the expression of oestrogen receptors (ERs) due to both endogenous and exogenous hormonal influence. Thus, the ER is increasingly expelled under the influence of oestrogen during the first half of the cycle. Under the influence of progesterone, the ER disappears during the luteal phase and is not even detectable after day 21. During menopause, the atrophic endometrium typically shows very little, if any, ER expression. In cases of oestrogen-induced hyperplasias, the receptor can again be demonstrated. The ER only disappears when nuclear irregularities occur in cases of adenomatous hyperplasia. In cases of invasive carcinoma, a heterogenous picture is seen which closely correlates with the degree of differentiation.