ESTROGEN AND PROGESTERONE-RECEPTOR EXPRESSION IN ENDOMETRIAL POLYPS

Endometrial polyps are a frequent cause of abnormal uterine bleeding, but their pathogenesis is poorly understood. This study was undertaken to investigate if endometrial polyps result from localized overexpres sion of estrogen receptors (ERs) or reduced expression of progesterone receptors (PRs). Fourteen cases of endometrial polyps, in which norma l cycling endometrium was also present on the same slide, were immunos tained for ERs and PRs. Percentages of positive cells in glands and st roma for each receptor were subjectively assessed to the nearest 5%. T he intensity of staining was recorded on a scale from 1+ to 4+. The le vel and intensity of staining in polyps were compared with the stainin g in normal endometrium. Fewer stromal cells in polyps expressed ERs a nd PRs compared with cycling endometrium (% ER = 55.9 +/- 25.8 vs. 74. 3 +/- 25.8, p = 0.03; % PR = 56.1 +/- 28.2 vs. 87.5 +/- 10.1, p = 0.00 2). Stroma in polyps also had significantly reduced intensity of stain ing for PRs, but not for ERs (intensity PR = 2.7 +/- 1.4 vs. 3.5 +/- 0 .7, p = 0.015; intensity ER = 2.1 +/- 0.7 vs. 2.4 +/- 0.8, p = 0.45). There were no significant differences in expression of ERs and PRs in the endometrial glands in endometrial polyps compared with normal endo metrium (% ER = 75.4 +/- 32.5 vs. 70.7 +/- 39.2, p = 0.25; % PR = 79.6 +/- 32.8 vs. 80.4 +/- 34.4, p = 0.8; intensity ER = 2.7 +/- 0.9 vs. 2 .4 +/- 1, p = 0.15; intensity PR = 2.9 +/- 1.4 vs. 3.4 +/- 0.7, p = 0. 15). We conclude that endometrial polyps may result from a decrease in ER and PR expression in stromal cells. Because of these receptor-nega tive stromal cells, endometrial polyps may be relatively insensitive t o cyclic hormonal changes.