Endometrial cancer is the most common tumor detected in the female reproductive system. The American Cancer Society estimates that more than 40,100 women are diagnosed with this disease each year in the United States. About one in 41 women will develop endometrial cancer during her lifetime.
Endometrial cancer — sometimes called uterine cancer — starts in the inner lining of the uterus, which is known as the endometrium. The uterus is a small, hollow, pear-shaped organ located in a woman's pelvis. The lower part of the uterus that extends into the upper end of the vagina is called the cervix. The upper part of the uterus, where a fetus grows after conception, is called the corpus.
The corpus is lined with the endometrium and is surrounded by a layer of muscular tissue called myometrium, which is where uterine sarcoma develops. (For more information about uterine sarcoma, visit the Leiomyosarcoma & Other Uterine Sarcomas section of this Web site.)
Endometrial cancer usually develops after menopause, between the ages of 50 and 60. Because it is frequently associated with postmenopausal bleeding, this kind of cancer is often found at its earliest stage, when it is highly curable.
Types of Endometrial Cancer
The vast majority of endometrial cancers — more than 75 percent — are adenocarcinomas, which form in the glandular cells located on the endometrium lining. Endometrioid adenocarcinomas are usually detected early and have a high rate of cure.
About 10 percent of endometrial cancers are papillary serous adenocarcinomas, and 5 percent are clear cell adenocarcinomas. Clear cell adenocarcinoma is a very rare form of uterine cancer that appears in women who were exposed in utero to an estrogen drug known as diethylstilbestrol (DES). From 1938 to 1971, DES was prescribed to some pregnant women to prevent miscarriage. The female children of these women have an increased risk of a rare type of cervical, uterine, or vaginal cancer.
Both papillary serous adenocarcinomas and clear cell adenocarcinomas are more-aggressive types of endometrial cancer, which are more likely to recur or spread (metastasize) to another part of the body.
Other types of endometrial cancer include adenosquamous carcinomas, which have elements of both adenocarcinoma and squamous cell carcinoma, and adenoacanthomas, in which squamous cells appear benign and glandular cells appear cancerous.