Common endometrial decidual reaction in postmenopausal breast cancer patients treated with tamoxifen and progestogens

In order to assess endometrial reaction to the combined treatment of tamoxifen and progestogens in asymptomatic postmenopausal breast cancer patients, we evaluated all such patients by vaginal ultrasonography and by histological examination of endometrial samplings. All patients were initially treated with tamoxifen, and progestogens were then added when metastases became evident. Of 12 patients included in the study, eight (66.66%) showed evidence of strong endometrial stromal decidualization, while three (25%) had decidual reactions in endometrial polyps. Overall, 11 (91.66%) of the patients had decidual reactions, and all were treated with progestogens for > or = 3 consecutive months. One patient, treated with progestogens for 1 months, had an inactive endometrium. All but three had thickened endometria (> 10 mm) on ultrasonographic evaluation. These data show that postmenopausal breast cancer patients who received progestogens for < or = 3 months, and who concomitantly took tamoxifen, had a uniform decidual reaction in all uteri.