Uterine cancer or womb cancer is any type of cancer that emerges from the tissue of the uterus. It can refer to several types of cancer, with cervical cancer (arising from the lower portion of the uterus) being the most common type worldwide and the second most common cancer in women in developing countries.
The terms uterine cancer and womb cancer may refer to any of several different types of cancer which occur in the uterus, namely:
1. Endometrial cancer:
- Endometrial carcinomas originate from cells in the glands of the endometrium (uterine lining). These include the common and readily treatable well-differentiated endometrioid adenocarcinoma, as well as the more aggressive uterine papillary serous carcinoma and uterine clear-cell carcinoma.
- Endometrial stromal sarcomas originate from the connective tissues of the endometrium, and are far less common than endometrial carcinomas.
- Malignant mixed Müllerian tumors are rare endometrial tumors which show both glandular (carcinomatous) and stromal (sarcomatous) differentiation – carcinosarcoma behaves similar to a high grade carcinoma, and it is felt to be of epithelial origin rather than true sarcoma.
2. Cervical cancer arises from the transformation zone of the cervix, the lower portion of the uterus and connects to the upper aspect of the vagina.
3. Uterine sarcomas: sarcomas of the myometrium, or muscular layer of the uterus, are most commonly leiomyosarcomas.
4. Gestational trophoblastic disease relates to neoplastic processes originating from tissue of a pregnancy that often is located in the uterus.
Causes of uterine cancer
It is not known with certainty what the causes for uterine cancer may be, though hormone imbalance is speculated as a risk factor. Estrogen receptors, known to be present on the surfaces of the cells of this type of cancer, are thought to interact with the hormone causing increased cell growth, which can then result in cancer. The exact mechanism of how this occurs is not understood.
Uterine Cancer Risk Factors
A woman's hormone balance plays a part in the development of most endometrial cancers. Many of the risk factors for endometrial cancer affect estrogen levels. Before menopause, the ovaries are the major source of the 2 main types of female hormones -- estrogen and progesterone.
Treating the symptoms of menopause with hormones is known as menopausal hormone therapy (or sometimes hormone replacement therapy). Estrogen is the major part of this treatment. Estrogen treatment can reduce hot flashes, improve vaginal dryness, and help prevent the weakening of the bones (osteoporosis) that can occur with menopause.
Doctors have found, however, that using estrogen alone (without progesterone) can lead to type I endometrial cancer in women who still have a uterus. To lower that risk , a progestin (progesterone or a drug like it) must be given along with estrogen. This approach is called combination hormone therapy.
Birth control pills
Using birth control pills (oral contraceptives) lowers the risk of endometrial cancer. The risk is lowest in women who take the pill for a long time, and this protection continues for at least 10 years after a woman stops taking this form of birth control. However, it is important to look at all of the risks and benefits when choosing a contraceptive method; endometrial cancer risk is only one factor to be considered. It's a good idea to discuss the pros and cons of different types of birth control with your doctor.
Total number of menstrual cycles
Having more menstrual cycles during a woman's lifetime raises her risk of endometrial cancer. Starting menstrual periods (menarche) before age 12 and/or going through menopause later in life raises the risk. Starting periods early is less a risk factor for women with early menopause. Likewise, late menopause may not lead to a higher risk in women whose periods began later in their teens.
The hormonal balance shifts toward more progesterone during pregnancy. So having many pregnancies protects against endometrial cancer. Women who have never been pregnant have a higher risk, especially if they were also infertile (unable to become pregnant).
A woman's ovaries produce most of her estrogen, but fat tissue can change some other hormones (called androgens) into estrogens. Having more fat tissue can increase a woman's estrogen levels, which increases her endometrial cancer risk. In comparison with women who maintain a healthy weight, endometrial cancer is twice as common in overweight women, and more than three times as common in obese women.
Tamoxifen is a drug that is used to prevent and treat breast cancer. Tamoxifen acts as an anti-estrogen in breast tissue, but it acts like an estrogen in the uterus. In women who have gone through menopause, it can cause the uterine lining to grow, which increases the risk of endometrial cancer.
A certain type of ovarian tumor, the granulosa cell tumor, often makes estrogen. Estrogen release by one of these tumors is not controlled the way hormone release from the ovaries is, and can sometimes lead to high estrogen levels. The resulting hormone imbalance can stimulate the endometrium and even lead to endometrial cancer. In fact, sometimes vaginal bleeding from endometrial cancer is the first symptom of one of these tumors.
Polycystic ovarian syndrome
Women with a condition called polycystic ovarian syndrome (PCOS) have abnormal hormone levels, such as higher androgen (male hormones) and estrogen levels and lower levels of progesterone. The increase in estrogen relative to progesterone can increase a woman's chance of getting endometrial cancer. PCOS is also a leading cause of infertility in women.
Using an intrauterine device
Women who used an intrauterine device (IUD) for birth control seem to have a lower risk of getting endometrial cancer. Information about this protective effect is limited to IUDs that do not contain hormones. Researchers have not yet studied whether newer types of IUDs that release progesterone have any effect on endometrial cancer risk. However, these IUDs are sometimes used to treat pre-cancers and early endometrial cancers in women who wish to preserve child-bearing ability.
The risk of endometrial cancer increases as a woman gets older.
Diet and exercise
A high-fat diet can increase the risk of several cancers, including endometrial cancer. Because fatty foods are also high-calorie foods, a high-fat diet can lead to obesity, which is a well-known endometrial cancer risk factor. Many scientists think this is the main way in which a high-fat diet raises endometrial cancer risk. Some scientists think that fatty foods may also have a direct effect on estrogen metabolism, which increases endometrial cancer risk.
Endometrial cancer may be as much as 4 times more common in women with diabetes. Diabetes is more common in people who are overweight, but even people with diabetes who are not overweight have a higher risk of endometrial cancer.
Endometrial cancer tends to run in some families. Some of these families also have an inherited tendency to develop colon cancer. This disorder is called hereditary nonpolyposis colon cancer (HNPCC). Another name for HNPCC is Lynch syndrome. In most cases, this disorder is caused by a defect in either the mismatch repair gene MLH1 or the gene MSH2. But at least 5 other genes can cause HNPCC: MLH3, MSH6, TGBR2, PMS1, and PMS2. An abnormal copy of any one of these genes reduces the body's ability to repair damage to its DNA or regulate cell growth. This results in a very high risk of colon cancer, as well as a high risk of endometrial cancer. Women with this syndrome have a 40% to 60% risk of developing endometrial cancer at some point. The risk of ovarian cancer is also increased. General information about inherited cancer syndromes can be found in Family Cancer Syndromes.
Breast or ovarian cancer
Women who have had breast cancer or ovarian cancer may have an increased risk of developing endometrial cancer, too. Some of the dietary, hormonal, and reproductive risk factors for breast and ovarian cancer also increase endometrial cancer risk.
Endometrial hyperplasia is an increased growth of the endometrium. Mild or simple hyperplasia, the most common type, has a very small risk of becoming cancerous. It may go away on its own or after treatment with hormone therapy. If the hyperplasia is called “atypical,” it has a higher chance of becoming a cancer. Simple atypical hyperplasia turns into cancer in about 8% of cases if it’s not treated. If it’s not treated, complex atypical hyperplasia (CAH) has a risk of becoming cancerous in up to 29% of cases, and the risk of having an undetected endometrial cancer is even higher. For this reason, CAH is usually treated.
Prior pelvic radiation therapy
Radiation used to treat some other cancers can damage the DNA of cells, sometimes increasing the risk of a second type of cancer such as endometrial cancer.