About the Uterus (Womb) and Endometrium
The uterus is a hollow organ, which is normally about the size and shape of a medium-sized pear. The uterus is where a fetus grows and develops when a woman is pregnant. The uterus (Womb) has two main parts.
- The Cervix is the lower end of the uterus that extends into the vagina.
- The upper part of the uterus is called the body or the corpus.
Although the Cervix is technically part of the uterus, when people talk about cancer of the uterus, they usually mean the body, not the cervix.
The body of the uterus has two main layers. The inner layer or lining is called 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, hormones cause the endometrium to change. During the early part of the cycle, before the ovaries release an egg (ovulation), the ovaries produce hormones called estrogens. Estrogen causes the endometrium to thicken so that it could nourish an embryo if pregnancy occurs. If there is no pregnancy, estrogen is produced in lower amounts, and more of the hormone called progesterone is made after ovulation. It prepares the innermost layer of the lining to shed. By the end of the cycle, the endometrial lining is shed from the uterus and becomes the menstrual flow (period). This cycle repeats until the women go through menopause (change of life).
Uterus and Endometrium Cancers
The two main types of cancer of the uterus are:
- Uterine sarcomas, which start in the muscle layer (myometrium) or supporting connective tissue of the uterus. These include uterine leiomyosarcomas and endometrial stromal sarcomas. These cancers are not covered here but are discussed in detail in Uterine Sarcomas.
- Endometrial carcinomas, which start in the cells of the inner lining of the uterus (the endometrium). Nearly all cancers of the uterus are this type. These cancers are the focus of the remainder of this information.
Endometrial carcinomas can be divided into different types based on how the cells look under the microscope (histologic types). These include:
- Adenocarcinoma, (most endometrial cancers are adenocarcinomas)
- Carcinosarcoma (discussed more below)
- Squamous cell carcinoma
- Undifferentiated carcinoma
- Small cell carcinoma
- Transitional Carcinoma
The most common type of adenocarcinoma is known as endometrioid cancer. Endometrioid cancer is made up of cells in glands that look much like the normal uterine lining (endometrium). Some of these cancers contain squamous cells (squamous cells are flat, thin cells that can be found on the outer surface of the cervix), as well as glandular cells. Cancer with both types of cells is called an adenocarcinoma with squamous differentiation. If under the microscope, the glandular cells look cancerous, but the squamous cells don’t, the tumor may be called an adenoacanthoma. If both the squamous cells and the glandular cells look malignant (cancerous), these tumors can be called adenosquamous (or mixed cell) carcinomas. There are other variants (or sub-types) of endometrioid cancers, such as secretory carcinoma, ciliated carcinoma, and villa glandular adenocarcinoma.
Clear-cell carcinoma, mucinous adenocarcinoma, and papillary serous adenocarcinoma. Are less common types of endometrial adenocarcinomas. These types tend to be more aggressive than most endometrial cancers. They tend to grow quickly and often have spread outside the uterus at the time of diagnosis.
Uterine carcinosarcoma (CS) starts in the endometrium and has features of both endometrial carcinoma and sarcoma. In the past, CS was considered a type of uterine sarcoma, but doctors now believe that CS is a carcinoma that is abnormal and so no longer looks much like the cells it came from (poorly differentiated).
Uterine CS is considered a type 2 endometrial carcinoma. CS tumors are also known as malignant mixed mesodermal tumors or malignant mixed muller Ian tumors (MMMTs). They make up about 4% of uterine cancers.
Signs and symptoms of Uterus or Endometrial Cancer
There are a few symptoms that may point to endometrial cancer, but some are more common as this cancer becomes advanced.