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Cancer occurs when cells undergo a change called a malignant transformation. They begin to grow and multiply without normal controls. As the cells grow and multiply, they form masses called malignant tumors or cancerous frowths or just cancers. A cancer can also spread or metastasize from their site of origin into the other tissues. Cancer is dangerous both because of its local growth and the damage it can cause and its potential for spread. Cancer growths overwhelm healthy cells by taking their space and the oxygen and nutrients they need to survive and function.
Ovarian cancer occurs when a tumor forms in one or both of a woman s ovaries. The ovaries are a pair of small organs that produce and release ova, or human eggs. The ovaries also produce important hormones such as estrogen and progesterone. They are located in the lower abdomen (pelvis), on either side of the womb (uterus). Ova released by the ovaries travel through the fallopian tubes to the uterus, where they may or may not be fertilized by the male sperm.
Not all transformations or changes are bad or malignant. A benign transformation can produce tumors. Benign tumors can grow in place, but do not have the potential to spread. The ovaries can develop benign tumors, as well as malignant tumors or cancers.
In the process called metastasis. malignant tumors may encroach on and invade neighboring organs or lymph nodes. or they may enter the bloodstream and spread to remote organs such as the liver or lungs. The presence of metastases or metastatic tumors is an ominous finding noted in the more advanced stages of cancer of the ovary.
The type of cell that originated the abnormal growth determines the class of the ovarian tumors.
- Epithelial tumors: These tumors arise from a layer of cells that line the ovary called the germinal epithelium. A majority of all ovarian cancers are epithelial. These are most common in women who have been through menopause (aged 45-70 years). These epithelial tumors are rarely found without at least some evidence of spread. Chemotherapy is used in addition to surgery to treat these cancers.
- Stromal tumors: Stromal tumors develop from connective-tissue cells that help form the structure of the ovary and produce hormones. Usually, only one ovary is involved. These account for 5-10% of ovarian cancers. These tumors typically occur in women aged 40-60 years. Often, surgical removal of the tumor is the only treatment needed. If the tumor has spread, though, the woman needs chemotherapy.
- Germ cell tumors: Tumors that arise from germ cells (cells that produce the egg) account for about 15% of all ovarian cancers. These tumors develop most often in young women (including teenaged girls). Although 90% of women with this type of cancer are successfully treated, many become permanently infertile .
- Metastatic tumors: Only 5% of ovarian cancers have spread from other sites to the ovary. The most common sites from which they spread are the colon. breast. stomach, and pancreas.
- Within these main classes are many different subtypes of tumors.
Noncancerous (benign) ovarian masses include abscesses or infections, fibroids, cysts, polycystic ovaries, endometriosis -related masses, ectopic pregnancies, and others.
- Of markedly enlarged ovarian masses ( 4 cm) found in women who are still menstruating (have not been through menopause ), about 20% are cancerous.
- Of markedly enlarged masses found in women who have been through menopause. about 45%-50% are cancerous.
The incidence of ovarian cancer varies greatly. Globally, Scandinavia, Israel, and North America have the highest rates. Developing countries and Japan have the lowest rates.
- Some 14,240 women in the U.S. die each year from ovarian cancer.
- The five-year survival rate is greater than 75% if diagnosis of the cancer occurs before it has spread to other organs. However, the five-year survival rate drops to 20% when the cancer has spread to the upper abdomen.
- In the United States, about one in 56 women develops cancer of the ovary. About 22,280 new cases in the U.S. are diagnosed each year.
What Are the Causes and Risk Factors for Ovarian Cancer?
In most ovarian cancer cases, no identifiable cause is present; however, family history does play a role.
- The lifetime risk for U.S. women of developing ovarian cancer is low.
- If one first-degree relative — a mother, sister, or daughter — has the disease, the risk increases.
- The risk can climb to 50% if two first-degree relatives have the disease.
- If a woman has ovarian cancer and her daughter develops ovarian cancer, the daughter will probably develop the cancer at a relatively young age (younger than 60 years).
Ovarian cancer has been linked with three hereditary syndromes.
- Breast-ovarian cancer syndrome
- Hereditary nonpolyposis colorectal cancer syndrome
- Site-specific ovarian cancer syndrome
Breast-ovarian cancer syndrome: A mutation in a gene called BRCA1 has been linked to increased risk of both breast and ovarian cancer.
- Some women who have this mutation develop ovarian cancer.
- Another mutation, involving the BRCA2 gene, also increases the risk of ovarian cancer but to a lesser degree.
- These mutations are hereditary, meaning that they can be passed from one generation to the next.
- Clues that may indicate the presence of these mutations include family members who have ovarian cancer or breast cancer (especially those who are diagnosed with these cancers when younger than 50 years), a relative with both breast and ovarian cancer, or a male relative with breast cancer .
- Development of more precise estimates of cancer risk and better genetic testing for carriers of these genes is taking place.
Hereditary nonpolyposis colorectal cancer (HNPCC) syndrome (Lynch syndrome II): This genetic syndrome has been dubbed family cancer syndrome and is associated with colon cancer developing in people younger than 50 years.
- Other organs that can be involved include the uterus, ovary, breast, stomach, and pancreas.
- A mutated gene causes this syndrome.
- Women with this syndrome have a chance of developing ovarian cancer.
Site-specific ovarian cancer syndrome: This is the least common of the three syndromes and experts don t know much about it, yet. This syndrome may be due to mutations of the BRCA1 gene.
Other factors that increase ovarian cancer risk include the following:
- Age greater than 50 years
- No pregnancies
- Use of fertility drugs: Some studies have shown that the use of fertility drugs increases the risk of ovarian cancer, but study results have not been consistent.
- Ashkenazi Jewish heritage
- European (white) heritage: White women are much more likely to have ovarian cancer than African American women.
- Asbestos exposure
- Repeated exposure of the genitals to talc
- Irradiation of the pelvic area
- Some viruses. especially the virus that causes mumps
Some findings suggest that estrogen may promote ovarian cancer in women who have been through menopause. For years, the cancer risks involved with using hormone replacement therapy divided the medical community. Research findings in 2002 and early 2003 showed that hormone replacement therapy does not provide many of the benefits it was believed to have, and it increases the risk of heart disease. Experts no longer routinely recommend long-term hormone replacement therapy for most women, though the issue can be considered on a case by case basis.
Some factors decrease ovarian cancer risk.
- Any factor that inhibits ovulation (release of an egg from the ovary) seems to protect against development of ovarian cancer. This may be because ovulation disrupts the epithelial layer of the ovary. As cells divide to repair the damage, uncontrolled division and malignant changes may occur.
- Term pregnancy (lasting the full nine months) significantly reduces the risk of ovarian cancer. As the number of pregnancies increases, the risk of ovarian cancer decreases.
- Use of oral contraceptives (birth control pills) reduces the risk of ovarian cancer.
- Breastfeeding lowers risk of ovarian cancer, and the risk decreases with increasing duration of breastfeeding.
- Removal of the ovaries before cancer reduces the risk of cancer arising in the ovaries to zero. However, cases of a closely related condition called primary peritoneal carcinoma due to embryonic remnants of ovarian formation can still occur. This may be a consideration in women with inherited cancer risks. Experts should base this decision on genetic testing and counseling.
- Having the woman s tubes tied (tubal ligation ) to prevent pregnancy.
- Having a hysterectomy lowers the risk of ovarian cancer.
Medically Reviewed by a Doctor on 11/30/2016
Robert P Edwards, MD