The uterus (womb) is a muscular organ within the pelvis. It has a cavity in the middle which is lined with tissue called the endometrium. Until the menopause, the endometrium builds up every month and is passed during a woman's period. Cancer of the uterus may develop if there are changes in the cells of endometrium during the last few years before the menopause or in the years just after. Cancer of the uterus should not be confused with cervical cancer, which is an entirely different condition.

This will vary according to whether or not the woman is still having periods. If she is still having periods then the cancer may make her periods more irregular or heavier. If her periods have stopped, then any bleeding from the vagina is abnormal and cancer of the womb needs to be considered as a possibility.

Any woman past the menopause should consult her doctor immediately if she has sudden and unexpected vaginal bleeding. The fact that cancer of the uterus often develops very slowly should not lead any woman to take any unexpected bleeding lightly.

Increased risk is also associated with the following:
Nulliparity (never having carried a pregnancy)
Infertility (inability to become pregnant)
Early menarche (onset of menstruation)
Late menopause (cessation of menstruation).

Women who have a history of endometrial polyps or other benign growths of the uterine lining, postmenopausal women who use estrogen-replacement therapy (specifically if not given in conjunction with periodic progestin), and those with diabetes are also at increased risk.

Tamoxifen, a drug used to treat breast cancer, may also increase the risk of developing endometrial cancer.