The potential oncogenic effect of tamoxifen on the endometrium

We report the case of an in-situ endometrial adenocarcinoma with severe aty pical hyperplasia which developed while the patient was on tamoxifen only 1 year after endometrial resection for benign pathology. A 55-year-old woman received tamoxifen as adjuvant therapy for breast cancer treated in 1994. At that time, a benign endometrial polyp was also removed before initiating tamoxifen treatment. In 1997, endometrial resection was performed for beni gn pathology (atrophic cystic endometrium). In 1998, an endometrial adenoca rcinoma was diagnosed. This case illustrates that endometrial resection doe s not protect women taking tamoxifen against subsequent development of seve re atypical lesions.