What is ovarian cancer?
Ovarian cancer is a malignant tumour in one or both ovaries. It can start in any of the three cell types found in the ovary.
Epithelial ovarian, fallopian tube and peritoneal cancers all develop in the same type of cell and are very similar. Recent research suggests that many epithelial ovarian cancers start in the fallopian tubes. Ovarian cancer often spreads from the ovaries to the diaphragm, the lining of the abdomen (peritoneum), and the sheet of fatty tissue that hangs inside the abdomen (omentum).
Learn more about:
- Who gets ovarian cancer?
- What types are there?
- What causes ovarian cancer?
- How important are genetic factors?
- The ovaries
Who gets ovarian cancer?
Each year, about 1400 Australian women are diagnosed with ovarian cancer. The average age at diagnosis is 63. It is the eighth most common cancer in women in Australia. Ovarian cancer is more commonly diagnosed in women over 50.
What types are there?
There are many types of ovarian cancer and the three most common types are listed below. Some women (usually younger women) are diagnosed with a borderline ovarian tumour. This is not considered to be cancer because, although it can spread, it does not usually invade other organs. For this reason, borderline tumours are also known as low malignant potential tumours.
- starts in the fallopian tubes, on the surface of the ovary (epithelium) or in the peritoneum
- most common type of ovarian cancer (about 9 out of 10 cases)
- subtypes include serous, mucinous, endometrioid and clear cell cancers
- usually develops in women over 60
- starts in the egg-producing (germinal) cells
- rare type of ovarian cancer (about 4% of cases)
- usually develops in adolescents and women under 40
Stromal cell (or sex cord-stromal tumours)
- rare cancer that starts in the cells that produce the female hormones oestrogen and progesterone
- usually occurs in women between 40 and 60
- may produce extra hormones, such as oestrogen
What causes ovarian cancer?
The causes of most ovarian cancers are unknown, but the risk factors include:
- age – ovarian cancer is most common in women over 50 and in women who have stopped menstruating (have been through menopause), and the risk increases with age
- genetic factors – up to 20% of serous ovarian cancers (the most common subtype) are linked to an inherited faulty gene, and a smaller proportion of other types of ovarian cancer are also related to genetic faults.
- family history – having one or more close blood relatives diagnosed with ovarian, breast, bowel or uterine cancers, or having Ashkenazi Jewish ancestry
- reproductive history – women who have not had children or who had children over the age of 35 may be slightly more at risk
- lifestyle factors – such as smoking and being overweight
- hormonal factors – including early puberty or late menopause, or using oestrogen-only hormone replacement therapy (HRT) for five years or more.
Some factors reduce the risk of developing ovarian cancer. These include having children, breastfeeding, using the combined oral contraceptive pill for several years, and having your fallopian tubes tied (tubal ligation) or removed.
How important are genetic factors?
Most women diagnosed with ovarian cancer do not have a family history of the disease.
Some women have an inherited faulty gene that increases the risk of developing ovarian cancer. However, not all women who inherit a faulty gene develop ovarian cancer, and not all women with an inherited faulty gene have a family history of cancer.
The main genetic condition known to increase the risk of ovarian cancer is hereditary breast/ovarian cancer, usually caused by a fault in the BRCA1 and BRCA2 genes. Less commonly, Lynch syndrome is associated with ovarian cancer. About 15–20% of women with ovarian cancer are found to have a fault in one of the BRCA genes or other similar genes.
Other genetic conditions continue to be discovered and are often included in genetic tests for cancer risk. Genetic testing aims to detect faulty genes that may increase the risk of developing cancer.
Many women diagnosed with ovarian cancer are eligible for a Medicare rebate for a genetic test. Your specialist or a familial cancer centre will assess your eligibility and, with your permission, order a blood test to check whether you have the BRCA1, BRCA2 or another similar mutation. Knowing whether you have a particular faulty gene may help determine suitable treatment options. See Targeted therapy for more information.
If the faulty gene causing the cancer is found, Medicare-funded testing can be offered to other family members who have no signs of cancer. For more information about genetic testing, talk to your specialist or local familial cancer centre, or call Cancer Council 13 11 20.
Listen to a podcast on Genetic Tests and Cancer.
The ovaries are part of the female reproductive system, which also includes the fallopian tubes, uterus (womb), cervix (the neck of the uterus), vagina (birth canal) and vulva (external genitals).
The ovaries are two small, grape-shaped organs. They are found in the lower part of the abdomen (the pelvic cavity). There is one ovary on each side of the uterus, close to the end of the fallopian tubes. Each ovary is made up of:
- epithelial cells – found on the outside of the ovary in a layer known as the epithelium
- germinal (germ) cells – found inside the ovaries, these cells eventually mature into eggs (ova)
- stromal cells – form connective (supporting) tissue within the ovaries, and produce the female hormones oestrogen and progesterone.
Each month, the ovaries release an egg (ovum) in a process called ovulation. The egg travels down the fallopian tube into the uterus. If the egg is fertilised by a sperm, it will implant itself into the lining of the uterus and grow into a baby. If the egg is not fertilised by a sperm, the lining is shed and flows out of the body through the vagina. This flow is known as a woman’s period (menstruation).
Oestrogen and progesterone cause ovulation and menstruation. As a woman gets older, the ovaries gradually produce less of these hormones. When the levels of oestrogen and progesterone fall low enough, a woman’s periods will become irregular and finally stop. This is known as menopause. After menopause, it is no longer possible to conceive a child. The ovaries also become smaller.
The female reproductive system