Noncontraceptive estrogens and abnormalities of endometrial proliferation.

Use of estrogen preparations among menopausal women has been causally associated with the development of hyperplasia and adenocarcinoma of the endometrium. The magnitude of the association seems to be greater for the hyperplastic and least aggressive malignant lesions, and smaller for tumors of higher stage and grade. This observed inverse relation of estrogen use to degree of malignancy is probably due to relatively early or overly liberal diagnoses of endometrial cancer among estrogen users, but could mean simply that estrogens promote less aggressive tumors. It appears the current increased incidence of endometrial cancer in the United States will not be followed by a corresponding increase in mortality from the disease.