Light micrograph showing atypical endometrial hyperplasia (which is synonymous with endometrial intraepithelial neoplasia) on the top and right (darker purple glands). Uterine hyperplasia is a reaction in the endometrium to excessive or uncoordinated ovarian hormone production. The result is that surface epithelial cells proliferate in both size and number. The centre and left portion of the image shows low-grade endometrioid carcinoma (lighter pink glands).