The endometrioid type of endometrial adenocarcinoma,(type 1-carcinoma) is estrogen-dependent and frequently associated with endometrial hyperplasia. The nomenclature of these hyperplasias is currently under discussion. The highest risk for metachronous carcinoma is associated with atypical hyperplasia of the endometrium as detected in fractional curettings. In postmenopausal patients treatment should consist of abdominal hysterectomy. The so-called type 2-carcinomas, serous-papillary and clear-cell type, do not demonstrate a similar association with precursor lesions. Pathological findings in patients treated with Tamoxifen include endometrial atrophy and fibro-cystic endometrial polyps, sometimes with cellular metaplasias. Patients with breast cancer and tamoxifen treatment have an increased risk of endometrial carcinoma. In some of these patients it could be argued whether the carcinoma has developed in a proceeding endometrial hyperplasia.