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Ovarian Cancer

Cancer is a group of many related diseases that begin in cells, the body's basic unit of life. To understand cancer, it is helpful to know about normal cells and what happens when they become cancerous.

The body is made up of many types of cells. Normally, cells grow, divide, and produce more cells when the body needs them. This orderly process helps to keep the body healthy. Sometimes, however, cells keep dividing when new cells are not needed. These extra cells form a mass of tissue, called a growth or tumor. Tumors can be benign or malignant.

Benign tumors are not cancer. They often can be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life.

Ovarian cysts are a different type of growth. They are fluid-filled sacs that form on the surface of an ovary. They are not cancer. Cysts often go away without treatment. If a cyst does not go away, the doctor may suggest removing it, especially if it seems to be growing.

Malignant tumors are cancer. Cells in these tumors are abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Cancer cells can also spread (metastasize) from their original site to other parts of the body.

A malignant tumor that begins in the ovaries is called ovarian cancer. There are several types of ovarian cancer. Ovarian cancer that begins on the surface of the ovary (epithelial carcinoma) is the most common type. This is the type of cancer discussed in this booklet. Ovarian cancer that begins in the egg-producing cells (germ cell tumors) and cancer that begins in the supportive tissue surrounding the ovaries (stromal tumors) are rare and are not discussed in this booklet. The Cancer Information Service and the other NCI sources listed under "National Cancer Institute Information Resources" can provide information or suggest resources that deal with these types of ovarian cancer.

Ovarian cancer cells can break away from the ovary and spread to other tissues and organs in a process called shedding. When ovarian cancer sheds, it tends to seed (form new tumors) on the peritoneum (the large membrane that lines the abdomen) and on the diaphragm (the thin muscle that separates the chest from the abdomen). Fluid may collect in the abdomen. This condition is known as ascites. It may make a woman feel bloated, or her abdomen may look swollen.

Ovarian cancer cells can also enter the bloodstream or lymphatic system (the tissues and organs that produce and store cells that fight infection and disease). Once in the bloodstream or lymphatic system, the cancer cells can travel and form new tumors in other parts of the body.

The exact causes of ovarian cancer are not known. However, studies show that the following factors may increase the chance of developing this disease:

Family history. First-degree relatives (mother, daughter, sister) of a woman who has had ovarian cancer are at increased risk of developing this type of cancer themselves. The likelihood is especially high if two or more first-degree relatives have had the disease. The risk is somewhat less, but still above average, if other relatives (grandmother, aunt, cousin) have had ovarian cancer. A family history of breast or colon cancer is also associated with an increased risk of developing ovarian cancer.

Age. The likelihood of developing ovarian cancer increases as a woman gets older. Most ovarian cancers occur in women over the age of 50, with the highest risk in women over 60.

Childbearing. Women who have never had children are more likely to develop ovarian cancer than women who have had children. In fact, the more children a woman has had, the less likely she is to develop ovarian cancer.

Personal history. Women who have had breast or colon cancer may have a greater chance of developing ovarian cancer than women who have not had breast or colon cancer.

Fertility drugs. Drugs that cause a woman to ovulate may slightly increase a woman's chance of developing ovarian cancer. Researchers are studying this possible association.

Talc. Some studies suggest that women who have used talc in the genital area for many years may be at increased risk of developing ovarian cancer.

Hormone replacement therapy (HRT). Some evidence suggests that women who use HRT after menopause may have a slightly increased risk of developing ovarian cancer.

About 1 in every 57 women in the United States will develop ovarian cancer. Most cases occur in women over the age of 50, but this disease can also affect younger women.

As we learn more about what causes ovarian cancer, we may also learn how to reduce the chance of getting this disease. Some studies have shown that breast feeding and taking birth control pills (oral contraceptives) may decrease a woman's likelihood of developing ovarian cancer. These factors decrease the number of times a woman ovulates, and studies suggest that reducing the number of ovulations during a woman's lifetime may lower the risk of ovarian cancer.

Women who have had an operation that prevents pregnancy (tubal ligation) or have had their uterus and cervix removed (hysterectomy) also have a lower risk of developing ovarian cancer. In addition, some evidence suggests that reducing the amount of fat in the diet may lower the risk of developing ovarian cancer.

Women who are at high risk for ovarian cancer due to a family history of the disease may consider having their ovaries removed before cancer develops (prophylactic oophorectomy). This procedure usually, but not always, protects women from developing ovarian cancer. The risks associated with this surgery and its side effects should be carefully considered. A woman should discuss the possible benefits and risks with her doctor based on her unique situation.

Having one or more of the risk factors mentioned here does not mean that a woman is sure to develop ovarian cancer, but the chance may be higher than average. Women who are concerned about ovarian cancer may want to talk with a doctor who specializes in treating women with cancer: a gynecologist, a gynecologic oncologist, or a medical oncologist. The doctor may be able to suggest ways to reduce the likelihood of developing ovarian cancer and can plan an appropriate schedule for checkups.

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