Ovarian cancer

What is ovarian cancer?

Ovarian cancer occurs when cells in one or both ovaries become abnormal, grow out of control and form a lump called a tumour. There are different types of ovarian cancer.

Sometimes an ovarian tumour is diagnosed as borderline (also known as a low malignant potential tumour). This is not considered to be cancer.

If ovarian cancer spreads beyond the ovaries, it often spreads to the organs in the abdomen.

Learn more about:

• Who gets ovarian cancer?
• What types are there?
• What causes ovarian cancer?
• Should I have genetic testing?
• The ovaries

Who gets ovarian cancer?

Each year, about 1400 Australians are diagnosed with ovarian cancer. It is more commonly diagnosed over the age of 50, but can occur at any age. It is the 10th most common cancer in women in Australia.

Anyone with ovaries can get ovarian cancer, so it mostly affects women. Transgender men and intersex people can also get ovarian cancer if they have ovaries. For information specific to your situation, speak to your doctor.

What types are there?

There are many forms of ovarian cancer. The three main types start in different types of cells: epithelial, germ or stromal cells.

Epithelial

• the most common type of ovarian cancer (about 9 out of 10 cases)
• starts on the surface of the ovary (epithelium)*
• subtypes include serous, mucinous, endometrioid and clear cell cancers
• mostly occurs over the age of 60

Germ cell

• rare type of ovarian cancer (about 4% of cases)
• starts in the egg-producing (germinal) cells
• mostly occurs under the age of 40

Stromal cell (or sex cord-stromal tumours)

• rare cancer that starts in the cells in the ovaries that produce the hormones oestrogen and progesterone
• may produce extra hormones, such as oestrogen
• mostly occurs between the ages of 40 and 60

* Epithelial cancer that starts in the fallopian tubes or in the peritoneum is very similar to epithelial ovarian cancer. Recent research suggests that many ovarian cancers start in the fallopian tubes.

What causes ovarian cancer?

The causes of most cases of ovarian cancer are unknown, but factors that can increase the risk include:

• age – ovarian cancer is most common in women over 50 and in women who have stopped having periods (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
• endometriosis – this condition is caused by tissue from the lining of the uterus growing outside the uterus
• reproductive history – women who have not had children, who have had assisted reproduction, or who have had children over the age of 35 may be slightly more at risk
• lifestyle factors – some types of ovarian cancer have been linked to smoking or being overweight
• hormonal factors – such as early puberty or late menopause. Some studies suggest that menopause hormone therapy (MHT), previously called hormone replacement therapy (HRT), may increase the risk of ovarian cancer, but the evidence is not clear.

Some factors reduce the risk of developing ovarian cancer. These include having children before the age of 35; breastfeeding; using the combined oral contraceptive pill for several years; and having your fallopian tubes tied (tubal ligation) or removed.

Should I have genetic testing?

Most women diagnosed with ovarian cancer do not have a family history of the disease, but some have inherited a faulty gene that increases the risk of developing ovarian cancer. Having an inherited faulty gene does not mean you will definitely develop ovarian cancer, and you can inherit a faulty gene without having a history of cancer in your family.

About 15–20% of women with ovarian cancer have an inherited fault in the BRCA1 or BRCA2 genes or other similar genes. The BRCA gene faults can also increase the risk of breast cancer.

Less commonly, a group of gene faults known as Lynch syndrome is associated with ovarian cancer and can also increase the risk of cancer of the bowel or uterus. As other genetic conditions are discovered, they may be included in genetic tests for cancer risk.

If you are diagnosed with ovarian cancer, your specialist or a family cancer centre will check if you need a blood test to look for a fault in the BRCA1, BRCA2 or another similar gene. This genetic test may be available through the public hospital system or with a Medicare rebate.

The results may help work out the best treatment for you. If a cancer-related gene fault is found, Medicare-funded testing may be offered to close adult female and male relatives to check their risk (men can inherit and pass on BRCA faults and may have a higher risk of prostate cancer).

For more information, listen to our podcast episode on genetic tests, and read Ovarian Cancer Australia’s booklet on Genetics and ovarian cancer.

The ovaries

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, walnut-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
• germ (germinal) cells – found inside the ovaries, and eventually mature into eggs (ova)
• stromal cells – form connective (supporting) tissue within the ovaries, and make the hormones oestrogen and progesterone.

At puberty, the ovaries begin releasing an egg (ovum) each month in a process known as 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 period or menstruation.

The hormones oestrogen and progesterone cause ovulation and menstruation. As you get older, the ovaries gradually produce less of these hormones. When the levels of oestrogen and progesterone fall low enough, periods become irregular and finally stop. This is known as menopause. After menopause, you can’t conceive a child naturally. The ovaries also become smaller.

The female reproductive system

Organs near the ovaries

Near the ovaries are many organs and other structures. These include the diaphragm (the sheet of muscle that separates the chest from the abdomen), the peritoneum (the lining of the abdomen) and the omentum (the sheet of fatty tissue that hangs like an apron inside the abdomen).