Does estrogen cause adenocarcinoma of the endometrium?

While the ability of estrogen to induce cancers in laboratory animals has been recognized for over 40 years, estrogen replacement therapy in menopausal women has been reported to be associated with an increased risk of endometrial adenocarcinoma only recently. The benefits that may result from estrogen replacement therapy, as detailed in previous articles, have been overshadowed by the emotional specter of cancer in the minds of many patients and physicians. This has occurred in spite of the facts that the reported increase in risk for the development of adenocarcinoma of the endometrium is relatively small and that adenocarcinoma of the endometrium tends to be the most easily cured gynecologic malignancy. The purpose of this article is to examine the biologic plausibility of an association between estrogen and endometrial adenocarcinoma, discuss the reports showing an increased risk of endometrial cancer, and mention the possible protective effect of progestins.