Uterine (Endometrial) Cancer - Causes

Authored by Dr Mary Harding, 01 Dec 2015

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The Information Standard

Reviewed by:
Dr Louise Newson, 01 Dec 2015

What is the womb?

The womb (uterus) is in your lower tummy (abdomen) behind your bladder. The inside of your uterus is where a baby grows if you become pregnant. The inside lining of your uterus is called the endometrium. This builds up and is then shed each month as a period in women who have not yet gone through the menopause. The thick body of the uterus is called the myometrium and is made of specialised muscle tissue.

Cross-section diagrams of the female reproductive organs detailing the uterus

The lowest part of your uterus is the neck of the womb (cervix) which pushes just into the top part of your vagina. At the top of your uterus are the right and left Fallopian tubes which carry the eggs (released from your ovaries) to inside your uterus.

What is cancer?

Cancer is a disease of the cells in the body. The body is made up from millions of tiny cells. There are many different types of cell in the body and there are many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply out of control.

A cancerous (malignant) tumour is a lump or growth of tissue made up from cancer cells which continue to multiply. Malignant tumours invade into nearby tissues and organs, which can cause damage.

Cancerous tumours may also spread to other parts of the body. This happens if some cells break off from the first (primary) tumour and are carried in the bloodstream or lymph channels to other parts of the body. These small groups of cells may then multiply to form secondary tumours (metastases) in one or more parts of the body. These secondary tumours may then grow, invade and damage nearby tissues and spread again.

Some cancers are more serious than others. Some are more easily treated than others (particularly if diagnosed at an early stage). Some have a better outlook (prognosis) than others. In each case it is important to know exactly what type of cancer has developed, how large it has become, and whether it has spread. This will enable you to obtain reliable information on treatment options and outlook.

See separate leaflet called What is Cancer? for more details about cancer in general.

What is uterine cancer?

Most uterine cancers develop from cells in the endometrium. The endometrium is the inside lining of the womb (uterus) and this cancer is called endometrial cancer. Cancer developing from muscle cells in the myometrium (uterine sarcomas) are rare and are not dealt with further in this leaflet. Cancer of the cervix (cervical cancer) is quite different to uterine cancer and is dealt with in a separate leaflet.

This leaflet deals only with endometrial cancer of the uterus.

What causes endometrial cancer?

A cancerous (malignant) tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply out of control. See separate leaflet called What Causes Cancer? for more details.

There are risk factors which are known to increase the risk of endometrial cancer developing. These include the following:

  • Increased exposure to oestrogen. Oestrogen is the main female hormone. Before the menopause the changing level of oestrogen together with another hormone, progesterone, causes the endometrium to build up each month and then be shed as a period. It is thought that factors which lead to prolonged higher-than-usual levels of oestrogen, or increased levels of oestrogen not being balanced by progesterone, may somehow increase the risk of endometrial cells becoming cancerous. These include:
    • If you have never had a baby. This is because your womb (uterus) has never had a rest from the rise of oestrogen that happens in the course of a normal monthly cycle.
    • If you are overweight or obese. This is because fat cells make oestrogen.
    • If you have certain rare oestrogen-producing tumours.
    • If you have a late menopause (after the age of 52) or started periods at a young age. This is because you will have more monthly menstrual cycles.
  • Endometrial hyperplasia. This is a non-cancerous (benign) condition where the endometrium builds up more than usual. It can cause heavy periods or irregular bleeding after the menopause. Most women with this condition do not develop cancer but the risk is slightly increased.
  • Tamoxifen. This is a drug which is used in the treatment of breast cancer. The risk of developing endometrial cancer from tamoxifen is very small - about 1 in 500. However, the benefits of taking tamoxifen usually outweigh the risks.
  • Diabetes. There is a small increased risk in women with diabetes.
  • Polycystic ovary syndrome. There is a very slight increased risk in women with this condition.
  • Genetic factors. 'Genetic' means that a condition is passed on through families through special codes inside cells called genes. Most cases of endometrial cancer are not due to genetic or inherited (hereditary) factors. However, in a small number of cases, a faulty gene (which can be inherited) may trigger the disease. This disorder is called hereditary nonpolyposis colon cancer (HNPCC).

Women who take the combined oral contraceptive pill actually have a lower risk of developing endometrial cancer.

Further reading and references

Women with endometrial cancer have a variety of symptoms that differ between individual women, and, after diagnosis, many women wish they had acted earlier on something they thought was irrelevant.If...

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