The ovaries are part of the female reproductive system. The female reproductive system also includes the fallopian tubes, uterus (womb), cervix (the neck of the womb) and vagina (birth canal).
The ovaries are two small, oval-shaped organs, each about 3 cm long and 1 cm thick in size. 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 covered by a layer of cells called the epithelium. Inside the ovaries are cells called germ cells, which will eventually mature into eggs (ova).
An egg, called an ovum, is released from one of the ovaries each month (ovulation). The egg travels down the fallopian tube to the uterus. If the egg is fertilised by sperm, it can grow into a baby. If an egg is not fertilised by sperm, it disintegrates and – with the lining of the uterus – passes out of the vagina in the monthly period (menstruation).
The ovaries also release the female hormones oestrogen and progesterone from cells called stromal cells.
As a woman gets older, the ovaries gradually produce less of the hormones oestrogen and progesterone. The production of mature eggs also decreases and the woman’s periods become irregular and finally stop. This is known as menopause, which usually happens between the ages of 45 and 55. After menopause, it is no longer possible to conceive a child naturally.
Ovarian cancer is a malignant tumour in one or both ovaries. Recent research suggests that many ovarian cancers start in the fallopian tubes. This is different to fallopian tube cancer, which is rare.
Each year, about 1400 Australian women are diagnosed with ovarian cancer. The average age at diagnosis is 64. It is the ninth most common cancer in women in Australia. Ovarian cancer is usually diagnosed in women over 501.
In its early stages, ovarian cancer usually has no symptoms or only vague ones. If symptoms occur, they may include: pressure, discomfort or pain in the abdomen or pelvis; swollen or bloated abdomen; appetite loss or feeling full quickly; changes in toilet habits (e.g. constipation, diarrhoea, passing urine often due to pressure, increased flatulence); heartburn and nausea; tiredness; unexplained weight loss or weight gain; changes in menstrual pattern or bleeding after menopause; or pain during sex.
If these symptoms are new for you or continue for a few weeks, make an appointment with your general practitioner (GP). Having these symptoms does not necessarily mean you have cancer, but it is best to have a check-up.
There are many types of ovarian cancer. The table below lists the three most common types.
Some women (usually younger women) are diagnosed with a borderline tumour. This is not considered to be cancer because, although it can spread, it does not invade other organs. For this reason, borderline tumours are also known as low malignant potential tumours.
The causes of ovarian cancer are unknown, but the risk factors include:
Some factors may 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).
Most women diagnosed with ovarian cancer do not have a family history of the disease.
About one in 10 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.
The two main genetic conditions known to increase the risk of ovarian cancer include hereditary breast/ ovarian cancer (fault in the BRCA1 and BRCA2 genes) and, less commonly, Lynch syndrome (formerly known as hereditary non-polyposis colorectal cancer or HNPCC).
Certain factors may increase the chance of ovarian cancer being hereditary, including if:
Cancer Australia has developed an online tool called the Familial Risk Assessment – Breast and Ovarian Cancer (FRA-BOC) to help health professionals assess your risk.
1. Australian Institute of Health and Welfare (AIHW), Australian Cancer Incidence and Mortality (ACIM) books: Ovarian cancer, AIHW, Canberra, 2016.