Endometrial carcinoma in a breast cancer patient treated with tamoxifen.

The use of tamoxifen for breast cancer therapy is linked to an increased danger of developing endometrial neoplasias in postmenopausal patients receiving the drug. Understanding the molecular mechanisms of the tumorigenic activity of tamoxifen may be of great prognostic and therapeutic significance. Our study suggests that tamoxifen treatment and alterations of the K-ras proto-oncogene may occur as parallel events in carcinogenesis of the endometrium.