What is endometrial cancer?
Endometrial cancer is a cancer that starts in the inner lining of the womb (uterus). This lining is called the endometrium. The pictures below show where the uterus is found and then provide a closer look at the uterus.
The uterus (womb) is a hollow organ, about the size and shape of a medium-sized pear. The uterus is where a fetus grows when a woman is pregnant. It has 2 main parts. The lower part, which extends into the vagina, is called the cervix. The upper part is the body of the uterus (also called the corpus). The body of the uterus has 2 layers. The inner layer is the endometrium. The outer layer of muscle is known as the myometrium. This thick layer of muscle is needed to push the baby out during birth. The tissue coating the outside of the uterus is the serosa.
During a woman's menstrual cycle this inner layer changes. In the early part of the cycle it gets thicker in case the woman becomes pregnant. If she does not become pregnant, the tissue is shed from the uterus and becomes the menstrual flow (period). This cycle repeats throughout a woman's life until change of life (menopause).
Types of cancers of the uterus and endometrium
Nearly all cancers of the uterus start in the endometrium. They are called endometrial carcinomas. Cancers can also start in the muscle layer of the uterus. These cancers belong to the group of cancers called sarcomas.
Cancers that start in the cervix are different from cancers that start in the body of the uterus. They are described in our document Cervical Cancer.
Cancers that start in the cells that line organs in the body are called carcinomas. Most endometrial cancers are not just carcinomas they are adenocarcinomas. This is a type of carcinoma that starts in the cells lining glands – such as the glands that line the uterus. The most common type of adenocarcinoma of the uterus is called endometrioid adenocarcinoma. There are other types that are far less common.
The grade of an endometrioid adenocarcinoma is based on how much the cancer cells form glands that look like the glands found in normal, healthy endometrium. In lower-grade cancers (grades 1 and 2), more of the cancer cells form normal-looking glands. In higher-grade cancers (grade 3), more of the cancer cells are kind of jumbled up and do not form normal glands. Higher grade cancers tend to grow faster and are more likely to spread than lower grade cancers.
Uterine carcinosarcoma (CS) is another cancer that starts in the endometrium and is covered here. When looked at under the microscope, this cancer looks like both endometrial carcinoma and sarcoma. It acts much like a high grade adenocarcinoma and is treated much the same way.
Less common uterine cancers that do not come from glandular tissue of the endometrium are called uterine sarcomas. These types of cancer are not covered here because their treatment and outlook for survival are different from the most common cancers of the endometrium. If you would like to know more about this type of cancer please see our document called Uterine Sarcoma.
Last Medical Review: 11/08/2013
Last Revised: 01/08/2015