Breast cancer is the most common cancer among women in the western world. The dramatic change in mortality due to breast cancer in the last decade was associated with better screening for early detection of malignancy and improved hormonal anti-estrogenic adjuvant therapy, mainly Tamoxifen. However, in the endometrium, Tamoxifen has a proestrogenic effect. Among women treated with Tamoxifen, a wide range of endometrial pathologies was documented--from polyps and hyperplasia to malignant tumors. Hence, there is still a debate on the character of malignant tumors developing under the influence of Tamoxifen treatment. Moreover, there are no clear guidelines considering the evaluation of the endometrium in women treated by Tamoxifen. These issues are discussed in this review.