Ovarian cancer is a disease in which malignant (cancer) cells form in the tissues of the ovaries.

The ovaries are a pair of organs in the female reproductive system. They are located in the pelvis, one on each side of the uterus (the hollow, pear-shaped organ where a fetus grows). Each ovary is about the size and shape of an almond. The ovaries produce eggs and female hormones (chemicals that control the way certain cells or organs function).

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Anatomy of the female reproductive system. The organs in the female reproductive system include the uterus, ovaries, fallopian tubes, cervix, and vagina. The uterus has a muscular outer layer called the myometrium and an inner lining called the endometrium.

See the following PDQ summaries for more information about ovarian cancer:

• Ovarian Cancer Prevention
• Genetics of Breast and Ovarian Cancer
• Ovarian Epithelial Cancer Treatment
• Ovarian Germ Cell Tumors Treatment
• Ovarian Low Malignant Potential Tumors Treatment

In the United States, ovarian cancer is the fifth leading cause of cancer death in women.

Ovarian cancer is also the leading cause of death from cancer of the female reproductive system. Since 1992, the number of new cases of ovarian cancer has gone down slightly. The number of deaths from ovarian cancer has slightly decreased since 2002.

Age and a family history of ovarian cancer can affect the risk of developing ovarian cancer.

Anything that increases your chance of getting a disease is called a risk factor. Risk factors for ovarian cancer include the following:

• Being older.
• Having a family history of ovarian cancer.
• Taking hormone replacement therapy after menopause.
• Using fertility drugs.
• Being taller than 5 feet 8 inches.
• Being obese.
• Having increased levels of CA 125.
• Having certain hereditary conditions, such as hereditary nonpolyposis colon cancer (HNPCC), also called Lynch Syndrome.
• Having certain changes in the BRCA1 or BRCA2 gene that are inherited (passed from the parent to the child).

Certain factors may decrease a woman's risk of developing ovarian cancer. Women who have taken oral contraceptives ("the pill"), given birth, breast -fed, or had a tubal ligation or hysterectomy have a lower than average risk of developing ovarian cancer. Prophylactic oophorectomy (removal of healthy ovaries) decreases ovarian cancer risk in women who have an altered gene related to breast cancer.