About ovarian cancer

Ovarian cancer starts when cells in one or both ovaries, the fallopian tubes or the peritoneum become abnormal, grow out of control and form a lump called a tumour. Cancer of the fallopian tube was once thought to be rare, but recent research suggests that many ovarian cancers start in the fallopian tubes. There are different types of ovarian cancer.

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

Sometimes an ovarian tumour is diagnosed as a borderline tumour (also known as a low malignant potential tumour). This tumour is not considered to be cancer but can still spread within the abdomen.

Learn more about:

• The ovaries
• What are the different types of ovarian cancer?
• Non-cancerous ovarian tumour
• Who gets ovarian cancer?
• What causes ovarian cancer?
• Does ovarian cancer run in families?

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 (belly). 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; eventually mature into eggs (ova)
• stromal cells – form connective (supporting) tissue within the ovaries, and make the hormones oestrogen and progesterone.

Menstruation – Each month, from puberty to menopause, the ovaries release an egg (ovum). This is known as ovulation. The egg travels from the fallopian tube to the uterus. If the egg is fertilised by a sperm, it attaches to the lining of the uterus and grows into a baby. If the egg is not fertilised, the lining of the uterus is shed and flows out of the body through the vagina. This flow is known as a period or menstruation.

Menopause – The hormones oestrogen and progesterone control ovulation and menstruation. As you get older, the ovaries gradually make less of these hormones. When the levels of oestrogen and progesterone fall low enough, periods finally stop. This is known as menopause. After menopause, you can’t have a child naturally.

The female reproductive system

Organs near the ovaries

Near the ovaries are many organs and other structures, including the:

• bladder – stores urine or wee
• small bowel – involved in digestion
• rectum – stores faeces or poo
• peritoneum – the lining of the abdomen
• omentum – the sheet of fatty tissue that hangs in front of the large bowel an apron.

What are the different types of ovarian cancer?

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

Non-cancerous ovarian tumour

Borderline tumour

• abnormal cells that form in the tissue covering the ovary
• doesn’t grow into the supportive tissue (stroma)
• grows slowly

Who gets ovarian cancer?

Each year, about 1720 Australians are diagnosed with ovarian cancer – this includes serous carcinomas of the fallopian tube. Over 80% of people diagnosed are over the age of 50, but ovarian cancer can occur at any age. It is the 9th most common cancer in females 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 you, speak to your doctor.

What causes ovarian cancer?

The causes of ovarian cancer are largely unknown, but factors that can increase the risk of developing ovarian cancer 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 (e.g. mother, sister) 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 (e.g. in-vitro fertilisation or IVF), or who have had children after 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.

Does ovarian cancer run in families?

Ovarian cancer most often occurs for unknown reasons. But some cases are due to an inherited faulty gene. 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% 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 developing 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 developing cancer of the bowel or uterus.

As other genetic conditions are discovered, they may be included in genetic tests for cancer risk. See Genetic testing after diagnosis.

For more on this, listen to our podcast on genetic tests and cancer below.

→ READ MORE: Ovarian cancer symptoms

Podcast: Genetic Tests and Cancer

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