Solution: When you identify endometrial thickening in a post-menopausal woman, there are three main differential possibilities: Endometrial cancer, endometrial hyperplasia, and an endometrial polyp. Endometrial hyperplasia is generally a diffuse process that have associated cystic spaces and often occurs in the peri or postmenopausal period. It is often associated with PCOS, or tamoxifen therapy. Endometrial polyps are usually more echogenic than the adjacent endometrium, often have a stalk and associated flow (although they can be broad-based), and can be multiple. Endometrial carcinoma starts focally and then spreads to be more diffuse. It invades the myometrium, resulting in an indistinct endometrial-myometrial interface. You might have been tricked into calling this case an endometrial polyp, but there are some worrisome findings in this case. The "lesion" is very irregular, while most polyps are very well defined. In addition, there is irregularity of the surrounding endometrium which is likely a manifestation of early spread along the endometrial surface. Biopsy and/or D and C would be needed for definitive evaluation.