It is in the endometrium, the uterus(womb) inner lining, where endometrial cancer begins. More about the endometrium and uterus:
- The uterus is approximately the shape and size of a medium-sized pear, and is a hollow organ. When a woman is pregnant, the uterus is where a fetus starts and grows. There are two main parts to the uterus(see below image):
- Extending into the vagina, is the uterus lower end, which is the cervix.
- The uterus upper part is called the corpus or the body.(The Latin word for body is corpus).
- Although technically a part of the uterus is the cervix, cancer of the uterus discussed by most people is not referring to the cervix, but to the body.
- There are two main layers to the body of the uterus. The endometrium is the lining or inner layer. The myometrium is the outer layer of muscle. Pushing the baby out during the birth process requires this thick layer of muscle. The serosa is the tissue that coats the outside of the uterus.
Hormones cause the endometrium to change, during the menstrual cycle of a woman. Prior to the ovaries releasing an egg(ovulation), during the early part of the cycle, hormones called estrogens are produced by the ovaries. So that if a pregnancy occurs it could nourish an embryo, estrogen causes the endometrium to thicken. Estrogen is produced in much lower amounts should there be no pregnancy, and made after ovulation is more of the hormone known as progesterone. This helps to prepare the lining’s innermost layer to shed. At the cycle’s end, shedding from the uterus and becoming the menstrual flow(period) is the endometrial lining. Until the woman goes through menopause(change of life), this cycle continues to repeat. This should give you an idea of what is endometrial cancer and how exactly it originates in the body.
Cancers of the endometrium and uterus
The uterus’s two main types of cancer are:
- Uterine sarcomas, which begin in the myometrium(muscle layer) or the uterus supporting connective tissue. Included in these are endometrial stromal sarcomas and uterine leiomyosarcomas. Although not covered here, these cancers are in detail discussed in Uterine Sarcomas.
- Endometrial carcinomas, which in the uterus inner lining or endometrium cells begin. Virtually all uterus cancers are this sort. The remainder of this information focuses on these cancers.
Based on how the cells under the microscope look(histologic types), endometrial carcinomas can be divided into different types. These include:
- Squamous cell carcinoma
- Carcinosarcoma(discussed further below)
- Adenocarcinoma,(adenocarcinomas are most endometrial cancers)
- Small cell carcinoma
- Undifferentiated carcinoma
- Transitional carcinoma
- Squamous cell carcinoma
Endometrioid cancer is the most common type of adenocarcinoma. Cells in the glands that appear much like the normal uterine lining or endometrium make up these endometrioid cancers. Squamous cells, which are thin, flat cells found on the cervix outer surface, are contained in some of these cancers, as well as glandular cells. An adenocarcinoma with squamous differentiation is what cancer with both types of cells is known as. The tumor may be called an adenoacanthoma, if the glandular cells under the microscope look cancerous, but the squamous cells do not. Should both the glandular cells and the squamous cells appear malignant(cancerous), adenosquamous(or mixed cell) is what these tumors may be called. Endometrioid cancers have other variants(or sub-types) such as villoglandular adenocarcinoma, ciliated carcinoma, and secretory carcinoma.
Less common types of endometrial adenocarcinomas are papillary serious adenocarcinoma, mucinous adenocarcinoma, and clear-cell carcinoma. As opposed to most endometrial cancers, these sorts have a tendency to be quite a bit more aggressive. They often spread at the time of diagnosis outside the uterus, and they tend to grow very quickly.
Endometrial Carcinoma Classifications
- It is based on their underlying causes and outlook that doctors sometimes classify endometrial carcinomas.
- It is on how many glands looking similar to those found in healthy, normal endometrium are formed, that the grade of endometrial cancer is based. More of the cancerous tissue forms glands, in lower-grade cancers. More of the cancer cells do not form glands, and are arranged in a disorganized or haphazard way, in higher-grade cancers.
- Tumors that are Grade 1 will have forming glands, 95% or more of the cancerous tissue.
- Tumors that are Grade 2 will have forming glands anywhere from 50% and 94% of the cancerous tissue.
- Tumors that are Grade 3 will have forming glands less than half of the cancerous tissue. “High-grade” is what Grade 3 cancers are called. They tend to have a poorer outlook than Grade 1 and 2(lower grade) cancers, and tend to be highly aggressive as well.
- It is thought to be excess estrogen that causes Type 1 endometrial cancers. It is sometimes in the endometrium an abnormal overgrowth of cells, or atypical hyperplasia, from which they develop(see the risk factors section). Type 1 cancers are typically on the slow side spreading to other tissues, and not very aggressive. Endometrioid cancers Grade 1 and Grade 2 are in fact “type.1” endometrial cancers
- A small number of endometrial cancers are made up of Type 2 endometrial cancer. Just what causes type 2 cancers experts are not sure of, but too much estrogen does not seem to be one of the causes. All endometrial carcinomas that aren’t type 1 are included in Type 2 cancers, such as undifferentiated carcinoma, clear-cell carcinoma, papillary serious carcinoma, and endometrioid carcinoma grade 3. These cancers are called “high-grade” or “poorly differentiated”, because they don’t look at all like normal endometrium. Type 2 cancers have a poorer outlook than type 1 cancers, because they are far more likely to grow outside the uterus and spread. Doctors are usually much more aggressive in treating these cancers.
- Uterine carcinosarcoma(CS) has features of both sarcoma and endometrial carcinoma, and starts in the endometrium. CS was thought to be a sort of uterine sarcoma in the past. Today, doctors believe CS is an abnormal carcinoma, and no longer resembles at all the cells from which it came(poorly differentiated).
- It is a type 2 endometrial carcinoma that Uterine CS is considered. CS tumors are also known as malignant mixed Mullerian tumors, or malignant mixed mesodermal tumors(MMMTs). About 4% of uterine cancers are made up by them.
Cancers that spread to the body of the uterus after beginning in the cervix are different from those which begin the uterus body; they are described in Cervical Cancer.