Normally, the lining of the uterus (endometrium) builds up and then sheds with each menstrual cycle. This shedding is menstrual bleeding, or a menstrual period.
But in most cases of endometrial cancer, the endometrium has built up and has not shed and thinned. The lining has remained thick. This is called endometrial hyperplasia. This is a "precancer" stage, and the cells can grow quickly and out of control. These fast-growing cells are cancer cells.
As the cancerous cells multiply, they form a mass of tissue, which can cause vaginal bleeding. Especially after menopause, this abnormal bleeding is a reason to call your doctor. Of women who have endometrial cancer after menopause, most have vaginal bleeding.
If endometrial cancer isn't treated, it may spread outside of the uterus. As it progresses, it may spread to the pelvic lymph nodes and other pelvic organs. Advanced-stage cancer may spread to lymph nodes and on to the lungs, liver, bones, brain, and vagina.1