Estrogen and progesterone receptors of adenomyosis in postmenopausal breast cancer patients treated with tamoxifen.

Adenomyosis is an ectopic endometrial tissue located in the myometrium. It has been reported to develop at a higher rate among postmenopausal breast cancer patients on tamoxifen (TAM) treatment than in untreated patients. It has also been reported to be stimulated by estrogen. Assessing receptor levels in adenomyotic tissue may indicate the adenomyotic cell's potential to interact with TAM. In the present study the estrogen receptor (ER) and progesterone receptor (PR) were analyzed by an immunohistochemical technique in adenomyotic and the corresponding endometrial tissues of 14 postmenopausal breast cancer patients treated with TAM and in 15 healthy postmenopausal patients who served as controls. All TAM-treated patients had normal postmenopausal serum estradiol levels. Overall the ER and PR contents in adenomyotic tissue (42.9 and 71.4%) and in the endometriotic tissue (64.3 and 78.6%) obtained from the study patients were similar to those obtained from the control group (adenomyosis, ER and PR = 46.7 and 86.7%; endometrium, ER and PR = 40 and 73.3%; p = NS). In the study group, the ER content was lower in the adenomyotic (42.9%) than in the endometriotic tissue (64.3%). No correlation was found between the duration of TAM therapy, the TAM dosage level or the ER or PR content in the adenomyotic or endometrial tissues. The finding of a relatively low ER content in the adenomyotic tissue than in the endometriotic tissue in postmenopausal TAM-treated patients without endogenous estrogens, similar to that observed in healthy premenopausal women, may be attributed to the estrogen-like effect of TAM.