Endometrial cancer refers to a type of cancer that originates in the endometrium, which is the inner lining of the uterus. This form of cancer can occur when cells within the endometrium grow abnormally and out of control, forming tumors or masses. Endometrial cancer is often referred to as uterine cancer because it affects the uterus. It typically occurs in women who have gone through menopause due to hormonal changes that can cause the endometrium to thicken and become irregular.