Endometriosis: The growth of endometrial tissue outside the uterus, causing pain and possibly affecting fertility. Endometrial Hyperplasia: Thickening of the endometrium, which can be a precursor to cancer. Endometrial Polyps: Small growths on the lining of the uterus, which can cause irregular bleeding. Endometrial Cancer: Cancer that originates in the lining of the uterus.