Endometrial Cancer Overview
The endometrium is the tissue lining the uterus (or womb). The uterus, a hollow organ about the size and shape of a pear, is found in a woman's pelvic region and is the organ where the fetus grows until birth. The upper part of the uterus is called the corpus; the lower, narrower part of the uterus is called the cervix. The cervix is the opening between the uterus and the vagina. The outer layer of the uterus is called the myometrium. The myometrium is thick and composed of strong muscles. These muscles contract during labor to push out the baby.
The endometrium is soft and spongy. Each month, the endometrium changes as part of the menstrual cycle. Early in the cycle, the ovaries secrete a hormone called estrogen that causes the endometrium to thicken. In the middle of the cycle, the ovaries start secreting another hormone called progesterone. Progesterone prepares the innermost layer of the endometrium to support an embryo should conception (pregnancy) occur. If conception does not occur, the hormone levels decrease dramatically. The innermost layer of the endometrium is then shed as menstrual fluid. This leads to the cyclical nature of the menstrual cycle.
Endometrial cancer occurs when cells of the endometrium undergo a transformation and begin to grow and multiply without the control mechanisms that normally limit their growth. As the cells grow and multiply, they form a mass called a tumor. Cancer is dangerous because it overwhelms healthy cells by taking their space and the oxygen and nutrients they need to survive and function.
Not all tumors are cancerous. Cancerous tumors are called malignant, meaning they can spread to other tissues and organs. Cancerous tumors may encroach on and invade neighboring organs or lymph nodes, or they may enter the bloodstream and spread to the bones or distant organs, such as the lungs. This process is called metastasis. Metastatic tumors are the most aggressive and serious of all tumors.
Two main types of endometrial cancers exist. Nearly all endometrial cancers are endometrial adenocarcinomas, meaning they originate from glandular (secreting) tissue. The other type of endometrial cancer, uterine sarcomas, originates in the connective tissue or muscle of the uterus. A subtype of endometrial adenocarcinomas, adenosquamous carcinoma, includes squamous cells (that is, the type of cells found on the surface of the skin and cervix). Other subtypes of endometrial adenocarcinomas are papillary serous adenocarcinomas and clear cell carcinomas. Because they are much more common than uterine sarcomas, endometrial adenocarcinomas are the focus of this article.
In developed countries, uterine cancer is the most common cancer of the female genital tract. In the United States, uterine cancer is the fourth most common cancer in women. Uterine cancer occurs in women of reproductive age and older. About one-quarter of cases occur before menopause, but the disease is most often diagnosed in women in their 50s or 60s.
Medically Reviewed by a Doctor on 6/2/2014
William T Creasman, MD
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