Endometrial cancer is the most common cancer of the reproductive organs among American women. It can often be cured, especially when diagnosed early. About 46,000 new cases of endometrial cancer are diagnosed every year in this country. Most women with endometrial cancer are diagnosed after menopause, although some women develop the disease earlier, around the time menopause begins.
What Is Endometrial Cancer? Is It the Same as Uterine Cancer?
The terms “endometrial cancer” and “uterine cancer” are sometimes used interchangeably, but they don’t mean exactly the same thing.
Endometrial cancer develops from a specific part of the uterus—the endometrium, which is the inner lining of the uterus. During your menstrual cycle, this lining thickens so it’s ready to support an embryo if your egg is fertilized. If the egg isn’t fertilized, the innermost layer of the endometrium is shed. This shedding is your menstrual flow. It’s regulated by the hormones estrogen and progesterone.
Most uterine cancers—more than 95 percent—start in the endometrium. These cancers are called endometrial cancers or endometrial carcinomas. (“Carcinoma” is the term for cancer that starts in one of the body’s linings.) Nearly all endometrial cancers start in the glandular cells of the endometrium. These cancers are called endometrioid adenocarcinomas.
Endometrial cancer occurs when cells in the endometrium begin to grow abnormally. They do not respond to regular cell growth, division, and death signals like they are supposed to. They also don’t organize normally. Instead they grow into a tumor, which may break through underlying layers of the uterus.
Cancer can also start in other parts of the uterus besides the endometrium, such as in the uterus’s thick outer layer of muscle (where it’s called uterine leiomyosarcoma) or in the connective tissue that supports the endometrium (where it’s called endometrial stromal sarcoma). These less common uterine sarcomas are discussed in the uterine sarcoma section.
Cancer can start in the cervix, the narrow part at the bottom of the uterus, too. This is referred to as cervical cancer, not uterine cancer.
Precancer—Complex Hyperplasia with Atypia
Many women who have symptoms of endometrial cancer (vaginal bleeding after menopause or abnormal menstrual bleeding) may have a biopsy that shows precancerous changes of the endometrium, called complex hyperplasia with atypia. Risk is high that 25 to 50 percent of these women will go on to develop endometrial cancer.
To reduce the risk, doctors usually advise women with this condition to have a hysterectomy (surgery to remove the uterus) if they are past childbearing years or do not intend to become pregnant. Many gynecologists refer these women to a gynecologic oncologist for their surgery because of the chance of finding true cancer at the time of the hysterectomy.
For younger patients who hope to preserve their ability to have children, doctors may sometimes take a more conservative approach, using hormone therapy (usually progestins) to reduce cancer risk and doing close follow-up to watch for any signs of cancer.