We don’t yet know exactly what causes most ovarian cancers. As discussed in the previous section, we do know some factors that make a woman more likely to develop epithelial ovarian cancer. Much less is known about risk factors for germ cell and stromal tumors of the ovaries.
There are many theories about the causes of ovarian cancer. Some of them came from looking at the things that change the risk of ovarian cancer. For example, pregnancy and taking birth control pills both lower the risk of ovarian cancer. Since both of these things reduce the number of times the ovary releases an egg (ovulation), some researchers think that there may be some relationship between ovulation and the risk of developing ovarian cancer.
Also, we know that tubal ligation and hysterectomy lower the risk of ovarian cancer. One theory to explain this is that some cancer-causing substances may enter the body through the vagina and pass through the uterus and fallopian tubes to reach the ovaries. This would explain how removing the uterus or blocking the fallopian tubes affects ovarian cancer risk. Another theory is that male hormones (androgens) can cause ovarian cancer.
Researchers have made great progress in understanding how certain mutations (changes) in DNA can cause normal cells to become cancerous. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually look like our parents because they are the source of our DNA. However, DNA affects more than the way we look. Some genes (parts of our DNA) contain instructions for controlling when our cells grow and divide. DNA mutations (defects) in these genes can lead to the development of cancer.
Inherited genetic mutations
A small portion of ovarian cancers occur in women with inherited gene mutations linked to an increased risk of ovarian cancer. These include mutations in the BRCA1 and BRCA2 genes, as well as the genes related to other family cancer syndromes linked to an increased risk of ovarian cancer, such as PTEN (PTEN tumor hamartoma syndrome), STK11 (Peutz-Jeghers syndrome), MUTYH (MUTYH-asociated polyposis, and the many genes that can cause hereditary nonpolyposis colon cancer (MLH1, MLH3, MSH2, MSH6, TGFBR2, PMS1, and PMS2). (These syndromes were discussed in the previous section).
Genetic tests can detect gene mutations associated with these inherited syndromes. If you have a family history of cancers linked to these syndromes, such as breast and ovarian cancers, thyroid and ovarian cancer, and/or colorectal and endometrial (uterine) cancer, you might want to ask your doctor about genetic counseling and testing. The American Cancer Society recommends discussing genetic testing with a qualified cancer genetics professional before any genetic testing is done. For more on this, see our document Genetic Testing: What You Need to Know.
Acquired genetic changes
Most DNA mutations related to ovarian cancer are not inherited but instead occur during a woman's life. In some cancers, acquired mutations of certain genes leading to the development of cancer may result from radiation or cancer-causing chemicals, but there is no evidence for this in ovarian cancer. So far, studies haven’t been able to specifically link any single chemical in the environment or in our diets to mutations that cause ovarian cancer. The cause of most acquired mutations remains unknown.
Most ovarian cancers have several acquired gene mutations. Research has suggested that tests to identify acquired changes of certain genes in ovarian cancers, like the TP53 tumor suppressor gene or the HER2 oncogene, can help predict a woman's prognosis. The role of these tests is still not certain, and more research is needed.
For more information about genetic changes that can lead to cancer, see our document Genes and Cancer.
Last Revised: 02/04/2016