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.

Carcinomas

Endometrial carcinomas are cancers that start in the cells that form the glands in the lining of the uterus. Most of these are adenocarcinomas. The most common type 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.

Uterine sarcomas

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.

Cervical cancers

Cancers that start in the cervix and then spread to the body of the uterus are different from cancers that start in the body of the uterus. They are described in our document, Cervical Cancer.