How cancer begins
The body is made up of millions of different cells. Cancer happens when some of the cells multiply in an abnormal way. When cancer affects organs and solid tissues, it causes a growth called a tumour to form. Cancer can occur in any part of the body where the cells multiply abnormally.
How cancer spreads
Left untreated, cancer can quickly grow and spread from the uterus into other tissues in the pelvis or to other parts of the body. This usually happens through the lymphatic system.
The lymphatic system is a series of glands that are spread throughout the body and linked together in a similar way to the blood circulation system. If you have a cold or flu, the glands that come up in the neck are the lymph glands (also called lymph nodes). The lymph glands produce many of the cells that are needed by your immune system.
Once the cancer reaches your lymphatic system, it can spread to any other part of your body, including your bones, blood and organs.
Risk factors for endometrial cancer
It is not known exactly what causes endometrial cancer, but a number of important risk factors have been identified. They are:
Age
The risk of developing endometrial cancer increases with age. Most cases of endometrial cancer develop in women who are over the age of 50.
Oestrogen
The risk of developing endometrial cancer is linked to the exposure of the body to oestrogen. Oestrogen is one of the hormones that regulates the reproductive system in women.
- Oestrogen stimulates the release of eggs from your ovaries and causes the cells of the womb lining (endometrium) to divide.
- Progesterone gets the lining of your uterus (the endometrium) ready to receive the egg from the ovaries.
The levels of oestrogen and progesterone in your body are usually balanced with each other. If oestrogen isn’t kept in balance by progesterone, the level in the body can increase, this is called unopposed oestrogen.
After the menopause, the body stops producing progesterone. However, there are still small amounts of oestrogen being produced. This unopposed oestrogen causes the cells of the endometrium to divide, and this can increase the risk of endometrial cancer.
Hormone replacement therapy (HRT)
Because of the link between increased levels of unopposed oestrogen and endometrial cancer, oestrogen-only hormone replacement therapy (HRT) should only be given to women who have had their womb surgically removed (hysterectomy).
In all other cases, both oestrogen and progesterone (combination HRT) must be used in HRT in order to reduce the risk of endometrial cancer.
Being overweight or obese
One way to assess whether your weight is healthy is to calculate your body mass index (BMI). This is your weight in kilograms divided by your height in metres squared. In the UK, people with a BMI of 25 to 30 are overweight, and those with an index above 30 are obese.
Being overweight or obese is a major risk factor for endometrial cancer, as this increases the level of oestrogen in your body while also reducing the protective effects of progesterone.
Women who are overweight are three times more likely to develop endometrial cancer compared with women who are a healthy weight. Women who are very obese (with a BMI of more than 40) are six times more likely to develop endometrial cancer compared with women who are a healthy weight.
Diabetes
Women who have diabetes are twice as likely to develop endometrial cancer as women without the condition. Diabetes causes an increase in the amount of insulin in your body, which in turn can raise your oestrogen level.
Reproductive history
Women who have not had children are at a higher risk of endometrial cancer. This may be because the hormonal changes that occur during pregnancy have a protective effect on the womb (increased levels of progesterone and decreased levels of oestrogen). It may also be because hormonal changes associated with some forms of infertility (for example polycystic ovary syndrome) are associated with a failure of ovulation, causing a decrease in the level of progesterone and thus an increase in the level of unopposed oestrogen.
Tamoxifen
Women who are treated with tamoxifen (a hormone treatment for breast cancer) can be at an increased risk of developing endometrial cancer. However, this risk is outweighed by the benefits that tamoxifen provides in preventing breast cancer.
Polycystic ovarian syndrome (PCOS)
Women with polycystic ovarian syndrome (PCOS) are at a higher risk of developing endometrial cancer. Women with PCOS have multiple cysts in the ovary, and this can cause symptoms such as irregular or light periods, or no periods at all, problems getting pregnant, weight gain, acne and excessive hair growth (hirsutism).
Endometrial hyperplasia
Endometrial hyperplasia is when the lining of the womb becomes thicker. Women with the condition may be at increased risk of developing endometrial cancer.
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