Oestrogen and progesterone receptors in endometriosis heterogeneity of different sites

The expression of receptors for the ovarian steroid hormones oestrogen and progesterone was studied immunohistochemically using monoclonal antibodies in samples of endometriosis and endometrium in 22 patients. In nine patients samples of endometriosis from more than one site were studied. There was marked heterogeneity in expression of receptors in endometriosis, both when comparing lesions with the corresponding endometrium and also between samples of endometriosis collected from different sites within the same patient. It was suggested that local environmental factors related to the site, depth and degree of fibrosis of the lesions determine the amount of steroid hormone stimulation reaching the lesions and account for the observed difference between endometriosis and endometrium and between endometriosis lesions of different sites.