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Types of Cancer > Gynecologic Cancers > Endometrial and Uterine Cancer > Overview
Endometrial Cancer: The Basics
Christopher Dolinsky, MD
Affiliation:
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: February 29, 2008
What is the endometrium?
The endometrium is the inner layer lining the uterus. The uterus is an organ that only women have, and it is where a baby grows and develops when a woman is pregnant. During pregnancy, the uterus undergoes an enormous increase in size. When a woman is not pregnant, the uterus is a small, pear-shaped organ that sits between a woman's rectum and her bladder. The cervix is the name for the lowest part of the uterus, and serves as the entrance to the uterus. There are two layers to the uterus: the myometrium, which is the outer, muscular layer, and the endometrium, the inner lining.. Every month that a woman is fertile and not pregnant, her ovaries release an egg that travels into her uterus and has the potential to become fertilized. During the few weeks leading up to an ovulation, a woman's endometrium thickens to provide a place for a fertilized embryo to grow and develop. If the egg is not fertilized, the endometrial lining is shed and together with the unneeded blood supply is passed through the birth canal (the woman's vagina). This is called menstruation. Two very important hormones, estrogen and progesterone, help regulate a woman's menstrual cycle and cause the endometrium to grow and thicken each month.
What is endometrial cancer?
Endometrial cancer develops when cells in the endometrium begin to grow out of control and can then invade nearby tissues or spread throughout the body. Large collections of this “out of control” tissue are called tumors. However, some tumors are not true cancers because they cannot spread or threaten someone's life. These are called benign tumors. The tumors that can spread throughout the body or invade nearby tissues are considered true cancers and are generally called malignant tumors. The distinction between benign and malignant tumors is very important in uterine cancer because there are many benign processes which affect the uterusand may get confused for cancers. Fibroids are very common benign tumors of the muscle of the uterus (myometrium), which are not cancerous. They can occasionally cause increased vaginal bleeding, vaginal discharge, or pain. Your doctor may suggest that you have your fibroids removed if they are becoming bothersome.
Cancers are characterized by the normal cells from which they form. The most common type of endometrial cancer is called endometrioid adenocarcinoma; it comes from cells that form glands in the endometrium, and it has a characteristic appearance under the microscope. Endometrioid endometrial cancer compromises about 75-80% of all endometrial cancers. The second most common form is papillary serous adenocarcinoma (about 10% of all endometrial cancers), and yet another form is clear cell adenocarcinoma (about 4-5% of all endometrial carcinomas). Both papillary serous and clear cell adenocarcinomas tend to be more aggressive than endometrioid adenocarcinomas, and are often detected at advanced stages. Sometimes an endometrial cancer has features of more than one subtype; this is called a mixed adenocarcinoma and they make up about 10% of all endometrial cancers. There are a few other rare types like mucinous adenocarcinoma and squamous cell adenocarcinoma that each compromise less than 1% of endometrial cancers.
Am I at risk for endometrial cancer?
Endometrial cancer is the most common gynecological malignancy in the United States. There were approximately 39,000 new cases diagnosed and 7,400 deaths attributed to endometrial cancer in 2007. There is a 2.6% chance of a woman developing endometrial cancer during her lifetime and it causes approximately 6% of all cancers in women.
The majority of women diagnosed with endometrial cancer have already gone through menopause, although it can occur in younger women as well. The average age of diagnosis isaround 60 years of age.Endometrial cancer is uncommon in women less than 40 years of age (5-10% of cases). It appears to be slightly more common in Caucasian women, but women of other races tend to present with more advanced disease.
Although there are several known risk factors for getting endometrial cancer, no one knows exactly why one woman gets it and another doesn't. One of the risk factors for developing endometrial cancer is age; the older a woman becomes, the higher her chances are of getting it. There appear to be two types of endometrial cancers: type I, which is estrogen-related and is more common (80% of cases), and type II, which does not appear to be estrogen-related and tends to present with more aggressive disease. For women with type I endometrial cancer, it appears that the amount of estrogen that a woman is exposed to in her lifetime influences her chances of contracting endometrial cancer. Women who are exposed to more estrogen, either naturally or from outside sources, are more likely to develop endometrial cancer. Thus, any factor that causes a woman to have high levels of estrogen is also a risk factor for endometrial cancer. The more menstrual cycles a woman has in her lifetime, the more estrogen to which her endometrium is exposed. Women who started menstruating early, go through menopause late, don't have any children, don't breastfeed, or don't use a form of birth control that stops ovulation (like birth control pills) are all potentially more likely to develop endometrial cancer. Another condition that increases estrogen in a woman's body is obesity. Fat tissue converts other hormones into estrogens, so extremely overweight people have higher levels of estrogen than thin people. This means that obesity is also a risk factor for endometrial cancer. Diabetes and high blood pressure (hypertension) (which also tends to occur in obese people) appear to be arisk factors for endometrial cancer as wellWomen who take hormone replacement therapy (HRT) after menopause are at a slightly increased risk for endometrial cancer. Tamoxifen is a drug that is used in women with breast cancer to decrease their risk of a cancer recurrence. Because it has estrogen-like properties, the use of tamoxifen is linked to higher rates of endometrial cancer. However, the danger is relatively small and tamoxifen is prescribed because the relative benefits of taking it (in terms of breast cancer prevention) outweigh the apparently minor increased risk of developing endometrial cancer.
Another risk factor for endometrial cancer is a family history of endometrial cancer. The greatest risk appears to be in first degree relatives (direct family members). A small percentage of women who get endometrial cancer carry a genetic mutation that causes a syndrome that increases their risk. The Lynch Syndrome is associated with colon and endometrial cancers (it is also called hereditary nonpolyposis colorectal cancer syndrome - HNPCC), Women can inherit a mutation from their parents and it may be worth testing for mutations if a woman has a particularly strong family history of endometrial or colon cancer (meaning multiple relatives affected, especially if they are under 50 years old when they get the disease). Having a mutation doesn't necessarily mean a woman is going to get the disease, but it does greatly increase her chances above the general population. Family members may elect to get tested to see if they carry mutations as well. If a woman does have the mutation, she can get more rigorous screening or even undergo a prophylactic hysterectomy (preventive removal of your uterus) to decrease her chances of contracting cancer. The decision to get tested is a highly personal one that should be discussed with a doctor who is trained in counseling patients about genetic testing. People with a history of breast cancer may also be at increased risk for endometrial cancer, but this is difficult to determine as many of the risk factors for breast and endometrial cancer overlap. As of yet, there has not been any association found between genes associated with breast cancer, such as the BRCA1 gene, and endometrial cancer, though studies are ongoing,
It has been demonstrated that a diet high in animal fats and low in fruits and vegetables can increase your risk for endometrial cancer. Remember that all risk factors are based on probabilities, and even someone without any risk factors can still get endometrial cancer. Talk to your doctor about your risk factors for endometrial cancer to understand his/her recommendations for screening and prevention.