Embarrassing Illnesses

Cancer is caused when the cells in a certain area of your body divide and multiply too rapidly. It is not fully understood why breast cancer occurs, but research into the causes of breast cancer is continuing.

So far, several likely causes have been identified,. The factors that increase your risk of developing the condition have also been identified. The various causes and risk factors are outlined below.

Age

Your risk of developing breast cancer increases as you get older. Breast cancer is most common among women over the age of 50 who have been through the menopause.

All women between the ages of 50 and 70 are entitled to be screened for breast cancer every three years as part of the NHS Breast Screening Programme. See Prevention, above, for more information about breast cancer screening.

Family history

Most breast cancer cases are not hereditary (run in families), although having a close relative with breast cancer can increase your chances of developing it. Particular genes, known as BRCA1 and BRCA2, can increase your risk of developing both breast and ovarian cancer, and these genes can be inherited. There is also a third gene associated with an increased risk of breast cancer, called TP53.

You have a higher than average risk of developing breast cancer if you have close relatives who have had breast or ovarian cancer. However, as breast cancer is the most common form of cancer in women, it can also occur more than once in the same family by chance.

If two or more close relatives from the same side of your family, such as your mother, sister or daughter, have had breast cancer, you may be eligible to be screened for breast cancer or for the genes that may make developing it more likely. See Prevention, above, for more information about breast screening.

Previous diagnosis of breast cancer

If you have had breast cancer before, you have a higher risk of developing it in your other breast. You should be closely monitored by your treatment team, such as your oncologist (specialist in cancer) and your breast nurse, so that any recurring cancer can be detected as soon as possible.

Previous benign breast lump

While having a benign breast lump does not mean that you have breast cancer, it can slightly increase your risk of developing it. Certain changes in your breast tissue, such as atypical hyperplasia (cells growing abnormally) or lobular carcinoma in situ (benign cell changes inside your breast lobes), can also make getting breast cancer more likely.

Research shows that having atypical hyperplasia can make you two to five times more likely to develop breast cancer. If you have atypical hyperplasia or lobular carcinoma in situ, your GP should monitor the health of your breasts with regular check-ups.

Always see your GP if you notice any lumps or changes in the appearance of your breasts.

Breast density

Your breasts are made up of thousands of tiny glands, or lobules, which produce milk, as well as fat and connective tissue. The glandular tissue contains a higher concentration of breast cells than the fat or connective tissue, making it denser. Therefore, having dense breast tissue can increase your risk of developing breast cancer because there are more cells that can become cancerous.

Dense breast tissue can also make a breast scan (mammogram) harder to read because it makes any lumps or areas of abnormal tissue harder to spot.

Despite the fact that breast cancer risk increases with age, younger women tend to have denser breasts. As you get older, the amount of glandular tissue in your breasts decreases and is replaced by fat, and your breasts become less dense.

Exposure to oestrogen

In some cases, breast cancer cells can be stimulated by the female hormone oestrogen. Your ovaries (where your eggs are stored) begin to produce oestrogen when you start puberty to regulate your periods.

Your risk of developing breast cancer may rise slightly with the amount of oestrogen that your body is exposed to. For example, if you started your periods at a young age and entered menopause at a late age, you will have been exposed to oestrogen over a longer period of time. Similarly, not having children or having children later in life may slightly increase your risk of developing breast cancer because your exposure to oestrogen is uninterrupted by pregnancy.

Being overweight or obese

If you have been through menopause and are overweight or obese, you may be more at risk of developing breast cancer. This is thought to be linked to the amount of oestrogen in your body, as being overweight or obese causes more oestrogen to be produced.

You can find out if you are overweight or obese by using the Healthy weight calculator.

Being tall

If you are taller than average, you are more likely to develop breast cancer than women who are shorter than average. The reason for this is not fully understood, although it may be because taller women tend to have more breast tissue than women who are of average or smaller height.

Alcohol

Your risk of developing breast cancer can increase with the amount of alcohol you drink. Research shows that there are three extra women diagnosed with breast cancer for every 200 women who regularly have two alcoholic drinks a day, compared with women who do not drink at all.

Radiation

Certain medical procedures which use radiation, such as X-rays and CT scans, may slightly increase your risk of developing breast cancer. However, the amount of radiation that is used during these procedures is always the lowest possible and they are only carried out when medically necessary.

If you had radiotherapy for Hodgkin's lymphoma when you were a child, you should have already received a written invitation from the Department of Health for a consultation with a specialist to discuss your increased risk of developing breast cancer. See your GP if you were not contacted or you did not attend a consultation. If you currently need radiotherapy for Hodgkin's lymphoma, your specialist should discuss the risk of breast cancer before your treatment begins.

Hormone replacement therapy (HRT)

Hormone replacement therapy (HRT) can cause a slightly increased risk of developing breast cancer. Both combined HRT and oestrogen-only HRT can increase your risk of developing breast cancer, although the risk is slightly higher if you take combined HRT.

The research behind this is still in its early stages, but it is estimated that there will be an extra 19 cases of breast cancer for every 1,000 women who are taking combined HRT for 10 years. The risk continues to increase slightly the longer you take HRT, but returns to normal once you stop taking it.