Tamoxifen treatment for breast cancer results in one-third of all patients developing endometrial polyps, hyperplasia, metaplasia, consistent with an estrogen-agonist effect. - GreenMedInfo Summary

OBJECTIVE: The aim of this study was the evaluation of endometrial histopathologic findings from 700 patients treated with tamoxifen (Tx) for breast cancer from two medical centers (United States and France). METHODS: A retrospective review of data including histologic slides from 134 hysterectomies and 566 endometrial biopsies from Tx-treated patients who presented with abnormal vaginal bleeding and/or abnormal sonograms was performed. Analysis of histologic characteristics included inactive/atrophic and functional endometria, endometrial polyps, hyperplasia and metaplasia, and endometrial cancer. Duration of Tx therapy was recorded when available, and its correlation with endometrial pathology was assessed. RESULTS: The only statistically significant difference between the data from the United States and France was the number of hysterectomies, which was almost double in France (27% vs 13.7%). Nonpathologic endometria made up 61.14% (inactive/atrophic 46%, functional 15.14%). Pathologic changes were found in 39.86% cases, of which polyps were 23.14%, glandular hyperplasia 8%, and metaplasia 3%; endometrial cancer made up 4.71% (33 cases). Nine cancers were well-differentiated endometrioid adenocarcinomas, and 24 were moderately or poorly differentiated, of which 13 had nonendometrioid components (serous, clear cell, MMMT). Fifteen cancers were found in endometrial polyps; 12 were invasive to the myometrium and 4 to blood vessels. The weight of the uteri exceeded 300 g in 15 cases, with 4 exceeding 900 g. The average age of all patients was 60.91 years and of the cancer patients alone it was 69.26 years. The shortest average duration of Tx therapy (2.5 years) was found in patients with inactive/atrophic endometria and the longest (6.8 years) in patients with endometrial cancer. Patients with endometrial polyps and cancer presented more often with abnormal vaginal bleeding than those with inactive/atrophic endometrium. CONCLUSIONS: Most Tx-treated patients had no pathologic endometrial changes. Endometrial polyps, hyperplasia, and metaplasia, consistent with an estrogen-agonist effect of Tx, were found in roughly one-third of all patients. The endometrial cancers were often high-grade and invasive tumors. Patients with endometrial pathology were more often symptomatic than patients with inactive/atrophic endometria.