Effects of hormone therapy on the endometrium.

Hormone therapy induces a variety of histologic changes in the endometrium. Histologic patterns encountered in the most commonly used hormonal regimens are described. Oral contraceptives are associated with inactive, atrophic, or pseudosecretory glands and edematous stroma, decidual reaction without spiral arterioles, and stromal granulocytes. A high-potency progesterone may induce marked stromal and vascular hyperplasia and stromal myomatous nodules. Ovulation induction therapy accelerates the maturation of the stroma and is often associated with a discrepancy between the glands showing early secretory changes and an edematous, decidualized stroma. Hormone replacement therapy may stimulate endometrial proliferation if estrogens are used alone and produce endometrial hyperplasia and neoplasia. When estrogen and progesterone regimens are used, a wide range of histologic pattern may be found in various combinations: proliferative and secretory endometrium, glandular and adenomatous hyperplasia, stromal hyperplasia and decidual transformation, glandular metaplasia, atrophic endometrium, and any of the above with endometrial atrophy. Progesterone therapy for endometrial hyperplasia and neoplasia is followed by secretory changes of the endometrium, mostly subnuclear vacuoles, decidual reaction, and sometime squamoid "morules." Secretory changes seen after progesterone therapy in the endometrium do not rule out residual carcinoma. For hormone therapy for breast carcinoma, tamoxifen acts as an antiestrogen on the breast but often acts as an estrogen agonist on the endometrium; tamoxifen therapy may be associated with endometrial hyperplasia, polyps, adenomyosis, adenomatous hyperplasia, and adenocarcinoma.