ABSTRACT
Tamoxifen is widely used for the treatment of breast cancer and currently proposed for preventive strategies. However. there is evidence that tamoxifen may affect other hormone sensitive organs, such as uterus and ovary. It has been documented that tamoxifen treatment is associated with development of endometrial polyp, endometrial hyperplasia, ovarian and endometrial cancer. Uterine malignant mixed mullerian tumor is a neoplasm which apparently arises from undifferentiated mullerian stroma and is composed of a mixture of malignant epithelial and stromal component. We report a case of malignant mixed mullerian tumor of uterus which was developed in a patient treated with tamoxifen for 5 years following a modified radical mastectomy due to breast cancer.