Overview
In the United States, the most common cancer of the female reproductive system is not the better-known ovarian cancer or cervical cancer; in fact, it is endometrial cancer, in which malignant cells grow in the endometrium, the lining of the uterus. This year, about 41,200 women in the United States will be diagnosed with cancer of the uterus and more than 95 percent of these cancers will be endometrial cancers. Uterine sarcomas are less common uterine cancers that do not come from tissue of the endometrium, but can involve the endometrium. These types of cancers are not covered here because treatment and survival rates are different from most common cancers of the endometrium.
Most endometrial cancers develop over a period of years and may develop from less serious problems of the lining of the uterus such as hyperplasia. The survival rate across all stages of endometrial cancer is approximately 84 percent, but if the cancer is diagnosed at its earliest stage, survival is 90 to 95 percent.
Fortunately, most endometrial cancers are discovered early because of warning signs such as irregular or postmenopausal bleeding. Therefore, it is important that physicians and women be aware of the significance of these signs. Although the majority of endometrial cancers occur in postmenopausal women, up to 25 percent may occur before menopause, so awareness is important throughout a woman's life.
Need-to-know anatomy
The female reproductive system produces female sex hormones called estrogen and progesterone, along with other hormones, that maintain the reproductive cycle by sending signals to the reproductive organs. The ovaries respond to these signals by producing eggs, which proceed to the fallopian tubes, the site of conception. If conception occurs, the embryo moves on to the uterus and implants in the endometrium, the uterine lining.
During a menstrual cycle, the endometrium changes so that it is prepared for an embryo if conception occurs. Near the beginning of the cycle, hormones stimulate the endometrium to thicken so it can nourish an embryo. At the middle of the cycle, if pregnancy does not occur, the hormones change and the top layer of the lining begins to die. At the end of the cycle, the dead tissue is shed from the uterus and becomes the menstrual flow. This cycle repeats throughout a woman's life until she begins menopause.
Causes
Like all cancers, endometrial cancer develops when abnormal cells grow out of control. Cancer cells develop because of damage to DNA-a substance in every cell that directs all activities. Damaged DNA can be inherited or a person's DNA can become damaged from an environmental exposure, like smoking. Normally, when DNA becomes damaged the body is able to repair it. In cancer cells, the damaged DNA is not repaired. It can grow and travel to other parts of the body and replace normal tissue. This is called metastasis (spread of cancer).
Risk Factors
Many factors influence the development of endometrial cancers. Risk factors for endometrial cancer include:
- Weight: Obesity (being overweight) is a risk factor because having more fat tissue can increase a woman's estrogen levels.
- Estrogen replacement therapy (ERT): This is used to offset the effects of menopause. Use of estrogen hormonal therapy without the use of progesterone increases a woman's risk of developing endometrial cancer.
- Tamoxifen: This is a drug that is used to treat breast cancer. Because the drug acts like estrogen in the uterus, it can cause the uterine lining to grow and increase the risk of developing endometrial cancer.
- Personal/Family History: A personal or family history of colon, endometrial, or ovarian cancer may indicate Lynch syndrome (hereditary nonpolyposis colorectal cancer syndrome). Women with Lynch syndrome have a very high risk of developing endometrial cancer.
- Age: As a woman ages, her chance of getting endometrial cancer increases. More than 95 percent of endometrial cancers occur in women age 40 and older.
- Diabetes: This is a risk factor for endometrial cancer whether or not a woman is obese.
- Ovarian diseases: Certain ovarian tumors produce estrogen and can cause an increase in estrogen levels.
- Complex atypical endometrial hyperplasia: This is a precancerous condition that may become cancerous if left untreated. Simple hyperplasia rarely becomes cancerous and can go away on its own or with hormonal treatment.
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