The endometrium in breast cancer patients on tamoxifen

We restudied histologically and immunohistochemically 17 endometrial carcin omas, 2 malignant mixed tumors and 180 endometria with benign changes durin g or after tamoxifen therapy. The carcinomas were subtyped according to the 1994 WHO-classification. Endometrial biopsies were taken only if the endom etrial thickness was > 8 mm sonographically, when a polyp was seen, or for postmenopausal bleeding. About half of the endometrial specimens showed sim ple or cystic atrophy, 55-76% had cystic-atrophic polyps or regressive hype rplasia. Depending upon the dose of tamoxifen, 7-19% (30 mg) to 27-36% (20 mg) showed moderate glandular proliferation. 20-33% had foci of mucinous, c lear cell or serous-papillary metaplasia. 68-70% revealed diffuse extensive fibrosis of the endometrial stroma. None of 11 patients biopsied before st arting tamoxifen therapy had advanced endometrial glandular proliferation i n the second endometrial biopsy after tamoxifen treatment. None of the 19 e ndometrial neoplasms after tamoxifen therapy was of the endometrioid type: 11 were mucinous adenocarcinomas, 4 clear cell carcinomas, 2 serous-papilla ry carcinomas, one carcinosarcoma and one malignant Mullerian mixed tumor. The reasons for discrepancies between suspicious sonograms and endometrial atrophy are discussed.