What is Endometrial Cancer?
Endometrial cancer begins when endometrial cells (the lining of the uterus) begin to grow out of control. Cells in almost any part of the body can become cancerous, and they can spread to other parts of the body. To learn more about how cancer begins and spreads, see What Is Cancer?
The uterus and endometrium cancer
The uterus is an empty organ, usually the size of a medium-sized uterus. The uterus is where the fetus grows and develops when the woman is pregnant. It has two main parts (see image below):
- The upper part of the uterus is called the body or body. (Corpus is the Latin word for body.)
- The cervix is the lower end of the uterus that connects to the vagina.
When people talk about cervical cancer, they usually mean cancer that starts in the body of the uterus, not the cervix. (Cervical cancer is a different type of cancer.)
The uterine body has two main layers:
- The myometrium is the outer layer. This thick layer of muscle is needed to push the baby out during birth.
- The endometrium is the inner layer. During menstruation in a woman, hormones cause the endometrium to change. Estrogen causes the endometrium to grow so that it can feed the fetus in the event of pregnancy. In the absence of pregnancy, estrogen is produced in small amounts and is made with a large hormone called progesterone. This causes the lining of the endometrium to rupture in the uterus and become a menstrual flow (period). This cycle also stops menstruating.
There is also a layer of tissue called the serosa that covers the outside of the uterus.
Types of endometrial cancer
Endometrial cancer (also called endometrial carcinoma) begins in the cells of the lining of the uterus (endometrium). This is the most common type of cancer in the uterus
Endometrial carcinomas can be classified according to the type of cells under a microscope. (These are called histologic forms.) Includes:
- Adenocarcinoma (most endometrial cancer is a type of adenocarcinoma called endometrioid cancer – see below)
- Uterine carcinosarcoma or CS (covered below grade)
- Squamous cell carcinoma
- Small cell carcinoma
- Temporary carcinoma
- Serous carcinoma
Clear-cell carcinoma, mucinous adenocarcinoma, differentiated carcinoma, dedifferentiated carcinoma, and serous adenocarcinoma are the most common types of endometrial adenocarcinomas. They tend to grow and spread faster than most types of endometrial cancer. They usually spread out of the uterus when they are found.
- Adenocarcinoma, (with amazing severity)
- Adenosquamous (or mixed cell)
- Secret carcinoma
- Ciliated carcinoma
- Villoglandular adenocarcinoma
Endometrial cancer implants
The stage of endometrial cancer is based on how well the cancer cells are organized into what look like glands found in the normal, healthy endometrium.
In low-grade cancers (marks 1 and 2), many cancer cells form glands. In advanced cancer (grade 3), most cancer cells are organized and do not form glands.
- Grade 1 tissue contains 95% or more of the cancerous tissues that make up the glands.
- Grade 2 tissue contains between 50% and 94% of cancer cells that make up the glands.
- Grade 3 plants have less than half of the cancerous tissues that make up the glands. Grade 3 cancer tends to be aggressive (it grows and spreads faster) and has a worse outlook than low-grade cancer.
Grade 1 and 2 endometrial cancer is a type 1 endometrial cancer. Type 1 cancer is usually less aggressive and does not spread to other tissues more quickly. Cancer type 1 endometrial cancer is thought to be caused by too much estrogen. They sometimes grow from atypical hyperplasia, abnormal growth of cells in the endometrium. (See Endometrial Cancer Risk Factors to find out more about this.)
A small amount of endometrial cancer is the second type of endometrial cancer. Type 2 cancer is more likely to grow and spread outside the uterus, they have poor vision (there is a type 1 cancer). Doctors tend to treat these cancers aggressively. They do not appear to be caused by too much estrogen. Types of type 2 cancers include all non-type 1 endometrial carcinomas, such as papillary serous carcinoma, clear-cell carcinoma, malignant carcinoma, and grade 3 endometrioid carcinoma. These cancers do not look at all like normal endometrium and are therefore not properly classified or advanced.
Uterine carcinosarcoma (CS) begins in the endometrium and has both endometrial carcinoma and sarcoma. (Sarcoma is cancer that starts in the cells of the uterus.) In the past, CS was considered a different type of cervical cancer called uterine sarcoma (see below), but doctors now believe that CS is a rare endometrial carcinoma. as the cells from which they came (well separated).
Uterine CS is a type of endometrial carcinoma. CS tissue is also known as mixed tissue or mixed Mullerian tissue (MMMTs). They make up about 3% of cervical cancer.
Other types of cancer in the uterus
Uterine sarcomas begin in the lining of the muscles (myometrium) or supporting tissues of the uterus. These include uterine leiomyosarcomas and endometrial stromal sarcomas. These cancers are not covered here but are discussed in detail in Uterine Sarcoma.
Cancer that starts in the cervix and then spreads to the uterus is different from cancer that starts in the cervix. Described in Cancer Cancer.