Endometrial cancer is a type of cancer that begins in the uterus. The uterus is the hollow, pear shaped pelvic organ in women where fetal development occurs. Endometrial cancer begins in the layer of cells that form the lining of the uterus. Endometrial cancer is sometimes called uterine cancer. Other types of cancer can form in the uterus, including uterine sarcoma, but they are much less common than endometrial cancer.