The aim of the present study is to report the clinicopathologic features of endometrial cancers subsequently develepod
after adjuvant treatment of breast cancer with tamoxifen. Seven endometrial cancers in tamoxifen-treated breast cancer
patients were treated at our institution between 1994 and 2002. Medical reports of the patients were evaluated
retrospectively. All patients were postmenopausal and one patient was nulliparous.
The age at discovery of the endometrial carcinoma ranged from 53-78. The menopausal age ranged from 40-53. Six of
seven postmenopausal patients had postmenopausal uterine bleeding as the initial complaint. Only one patient was
found to have endometrial cancer at annual gynecologic examination. Endometrial neoplasia was diagnosed by dilatation
and curettage in all cases. The patients had been treated with 20 mg of tamoxifen daily for 1-14 years. Six patients were
found to have endometrial carcinoma during adjuvant tamoxifen treatment. Only one patient developed endometrial
carcinoma six years after the cessation of adjuvant tamoxifen treatment. Histopathologic examination of the specimens
revelaed five cases of adenocarcinoma and two cases of sarcoma. Malignant mixed mesodermal tumor and
adenosarcoma of the endometrium developed in long-term tamoxifen users (8 and 14 years, respectively).
Patients with breast cancer using adjuvant tamoxifen treatment, especially the long-term users should be monitored for
the possibility of endometrial neoplasia. It is notable that five out of seven endometrial malignancies were not of