Endometrial cancer, also called uterine cancer, is the abnormal growth of cells in the lining of the uterus (endometrium). The cause of endometrial cancer is not known, but exposure over many years to the hormone estrogen without enough of the hormone progestin to balance it (unopposed estrogen) is linked with type I endometrial cancer.

Long-term unopposed estrogen exposure can be caused by:

• Obesity. Fat cells make extra estrogen, but the body doesn't make extra progesterone to balance it out.
• Beginning menstruation before age 12 or starting menopause after age 55.
• Taking tamoxifen.
• Long menstruation span (from first period to menopause).
• Never having been pregnant or completed a full-term pregnancy.
• Never having breast-fed.
• Using estrogen replacement therapy without the addition of the hormone progestin.

Symptoms of endometrial cancer include heavy or unusual vaginal bleeding, especially after menopause but also near the time that menopause begins.

Endometrial cancer is usually treated with surgery to remove the uterus (hysterectomy). It may also be treated with radiation therapy, hormone therapy, and chemotherapy.