Ovarian cancer

Ovarian cancer overview

Cancer occurs when cells undergo a transformation and begin to grow and multiply without normal controls. As the cells grow and multiply, they form masses called tumours. Cancer is dangerous because it overwhelms healthy cells by taking their space and the oxygen and nutrients they need to survive and function.

Ovarian cancer occurs when a tumour forms in one or both of a woman's ovaries. The ovaries are a pair of small organs that produce and release ova, or human eggs. The ovaries also produce important hormones such as oestrogen and progesterone. They are located in the lower abdomen (pelvis), on either side of the womb (uterus). Ova released by the ovaries travel through the fallopian tubes to the uterus, where they may or may not be fertilised by the male sperm.

Cancerous tumours are malignant. This means they may spread to other tissues and organs.

In a process called metastasis, malignant tumours may intrude on and invade neighbouring organs or lymph nodes, or they may enter the bloodstream and spread to remote organs, such as the liver or lungs. Metastatic tumours are the most aggressive and serious of all tumours.

The type of cell where the abnormal growth originated determines the class of the ovarian tumours.

• Epithelial tumours: These tumours arise from a layer of cells that surrounds the outside of the ovary called the germinal epithelium. About 70%-80% of all ovarian cancers are epithelial. These are most common in women who have been through the menopause (between 45-70 years).
• Stromal tumours: Stromal tumours develop from connective-tissue cells that help form the structure of the ovary and produce hormones. Usually, only one ovary is involved. These account for 5%-10% of ovarian cancers. These tumours typically occur in women between the ages of 40 and 60 years.
• Germ cell tumours: Tumours that arise from germ cells (cells that produce the egg) account for about 15% of all ovarian cancers. These tumours develop most often in young women (including teenage girls). Although 90% of women with this type of cancer are successfully treated, many become permanently infertile.
• Metastatic tumours: Only 5% of ovarian cancers have spread from other sites. The most common sites from which they spread are the colon (52%), breast (17%), stomach (10%) and pancreas (5%).

Within these main classes are many subtypes of tumours.

Non-cancerous (benign) ovarian masses include abscesses, cysts, polycystic ovaries, endometriosis-related masses, ectopic pregnancies and others.

• Of markedly enlarged ovarian masses (>4cm) found in women who are still menstruating (have not been through the menopause), about 20% are cancerous.
• Of markedly enlarged masses found in women who have been through the menopause, about 45%-50% are cancerous.

Ovarian cancer causes

In 95% of ovarian cancer cases, no identifiable cause is present, however family history does play a role.

• The lifetime risk for women in the UK of developing ovarian cancer is around 2%.
• If one first-degree relative - a mother, sister or daughter - has the disease, the risk increases.
• If two first-degree relatives have the disease the risk increases further.
• If a woman has ovarian cancer and her daughter develops ovarian cancer, the daughter will probably develop the cancer at a relatively young age (younger than 60 years).