Breast Screening


About 1 in 8 women in the UK are diagnosed with breast cancer during their lifetime. There's a good chance of recovery if it's detected in its early stages.

Breast screening aims to find breast cancers early. It uses an X-ray test called a mammogram that can spot cancers when they are too small to see or feel.

Breast screening does, however, have some risks you should be aware of (see below).

As the likelihood of getting breast cancer increases with age, all women who are aged 50-70 and registered with a GP are automatically invited for breast cancer screening every three years.

In the meantime, if you are worried about breast cancer symptoms, such as a lump or area of thickened tissue in a breast, don't wait to be offered screening – see your GP.

This page gives an overview of breast cancer screening, with links to information on why and when it is offered, what happens when you go for breast screening, and receiving your results.

Why its offered

The NHS offers screening to save lives from breast cancer. Screening does this by finding breast cancers at an early stage, when they are too small to see or feel.

However, it does have some risks. Some women who have screening will be diagnosed and treated for breast cancer that would never otherwise have caused them harm.

Screening does not prevent you from getting breast cancer, and it may not help if you already have advanced stage breast cancer.

It's up to you to decide if you want to have breast screening.

Benefits of breast screening

Most experts agree that regular breast screening is beneficial in identifying breast cancer early. The earlier the condition is found, the better the chances of surviving it.

You're also less likely to need a mastectomy (breast removal) or chemotherapy if breast cancer is detected at an early stage.

Risks of breast screening:


Some women who have screening will be diagnosed and treated for breast cancer that would never otherwise have caused them harm. Read about breast cancer treatment, including potential side effects.

Unnecessary distress

Following screening, about one in 25 women will be called back for further assessment. Being called back doesn't mean you definitely have cancer. The first mammogram may have been unclear.

Most women who receive an abnormal screening result are found not to have breast cancer. These women may experience unnecessary worry and distress.

About 1 in 4 women who are called back for further assessment are diagnosed with breast cancer.

Missed diagnosis

There's a small chance that you'll receive a negative (all clear) mammogram result when cancer is present. Breast screening picks up most breast cancers, but it misses breast cancer in about one in 2,500 women screened.


A mammogram is a type of X-ray, and X-rays can, very rarely, cause cancer.

During a mammogram, your breasts are exposed to a small amount of radiation (0.4 millisieverts, or mSv).

For comparison, in the UK, a person receives a dose of 2.2 mSv a year from natural background radiation. However, the benefits of screening and early detection are thought to outweigh the risks of having the X-ray.

Weighing up the possible benefits and risks of breast screening

There is debate about how many lives are saved by breast screening and how many women are diagnosed with cancers that wouldn't have become life-threatening. The numbers below are the best estimates from a group of experts who have reviewed the evidence.

Saving lives from breast cancer

Screening saves about one life from breast cancer for every 200 women who are screened. This adds up to about 1,300 lives saved from breast cancer each year in the UK.

Finding cancers that would never have caused a woman harm

About three in every 200 women screened every three years from the age of 50 to 70 are diagnosed with a cancer that would never have been found without screening and would never have become life-threatening. This adds up to about 4,000 women each year in the UK who are offered treatment they did not need.

What this means

Overall, for every 1 woman who has her life saved from breast cancer, about 3 women are diagnosed with a cancer that would never have become life-threatening.

Researchers are trying to find better ways to tell which women have breast cancers that will be life-threatening and which women have cancers that will not.

When its offered

In Wales women aged between 50-70, who are registered with a GP, are automatically invited for screening every three years. You should receive your first invitation for screening by the time you are 52 years of age.  Women over the age of 70 are still eligible to be screened and can arrange this through their GP or local Breast Test Wales screening centre.

Screening takes place at a special clinic or mobile breast screening unit.  A mammogram (X-ray of the breast) is taken by a female health professional. The mammogram is then studied to look for any abnormalities. The aim is to find breast cancer at an early stage, when any changes in the breast would be too small to feel and when there is a good chance of successful treatment and full recovery.

Not all cancers are found during breast screening. Breast cancer can develop between screening appointments. Even if you go to breast screening, it is important to get to know your breasts so that you can spot any unusual changes early on and report them to your GP.

If you have a family history of breast cancer

If you think you may have an increased risk of breast cancer because you have a family history of breast cancer (female or male) or ovarian cancer, talk to your GP so you can be referred to a hospital high-risk clinic. The clinic may refer you for genetic testing, if they feel it is appropriate.

Screening for women at high risk of breast cancer

If you've been found to have an increased risk of developing breast cancer, you may have yearly magnetic resonance imaging (MRI) scans or mammograms, depending on your age and your specific level of risk. MRI scans are sometimes used instead of mammograms, because they're better at detecting cancer if you have dense breast tissue.

What happens at the screening unit?

Screening is carried out by female staff, who take mammograms to detect abnormalities. The breasts are X-rayed one at a time. The breast is placed on the X-ray machine and gently but firmly compressed with a clear plate. Two X-rays are taken of each breast at different angles.

Most women find the compression uncomfortable and occasionally it may be painful. However, the compression is necessary to ensure the mammogram is clear. Any discomfort will be over quickly.

The whole appointment takes less than half an hour and the mammogram only takes a few minutes. The results of the mammogram will be sent to you and your GP.


Your breast cancer screening results

After your breasts have been X-rayed, the mammogram will be checked for any abnormalities. About 1 in 25 women will be called back for further assessment.

Being called back doesn't mean you definitely have cancer. The first mammogram may have been unclear.

About 1 in 4 women who are called back for further assessment are diagnosed with breast cancer.

You will receive a letter with your breast screening results within two weeks of your appointment. The results will also be sent to your GP.

Most women will have a satisfactory result

In about 96 out of every 100 women screened, the mammogram will show no sign of cancer. This is a satisfactory result.

Remember that cancer can still develop between mammograms, so tell your GP straight away if you notice any breast changes. Read about the symptoms of breast cancer.

Some women will need more tests because they have an abnormal result

The results letter may say you need more tests because the mammogram looks abnormal. About 4 in every 100 women are asked to come back for more tests after screening.

Out of these 4 women, 1 will be found to have cancer. The rest will not have cancer and will go back to having screening invitations every three years.

If you are called back for more tests, you may have a breast examination, more mammograms and ultrasounds. You may also have a biopsy, which is when a small sample is take from your breast with a needle to be checked under a microscope. You will usually get your results within a week.

Occasionally, women will need another mammogram before they get their result

Sometimes technical problems mean that the mammogram is not clear enough to read. If this happens, you will be asked to have another mammogram to get a clearer picture of your breast.

If you're found to have breast cancer...

If you're found to have breast cancer, it could be either non-invasive or invasive.

Non-invasive breast cancer

About one in five women diagnosed with breast cancer through screening will have non-invasive cancer. This means there are cancer cells in the breast, but they are only found inside the milk ducts (tubes) and have not spread any further. This is also called ductal carcinoma in situ (DCIS).

In some women, the cancer cells stay inside the ducts. But in others, they will grow into (invade) the surrounding breast in the future.

Doctors can't tell whether non-invasive breast cancers will grow into the surrounding breast or not.

Invasive breast cancer

About 4 in 5 women diagnosed with breast cancer through screening will have invasive cancer. This is cancer that has grown out of the milk ducts and into the surrounding breast. Most invasive breast cancers will spread to other parts of the body if left untreated.

Read about the treatment of both invasive and non-invasive breast cancer.

Frequently asked Questions

In this section you can find the answers to some of the most frequently asked questions about breast screening.

I haven't been called for breast screening even though I'm over 50 – do I need to contact anyone?

The NHS Breast Screening Programme is a rolling one, which calls women from doctors' practices in turn. This means not every woman receives her invitation as soon as she is 50. It will be sometime between the ages of 50 and 53.

If you are registered with a GP and the practice has your correct details, you will automatically receive an invitation. You don't need to contact anyone but you might like to ask your surgery when the women on their list are next due for screening.

I've found a lump in my breast – can you tell me how I can get a mammogram?

The NHS Wales Breast Screening Programme is a population screening programme which invites all women aged 50 to 70 as a matter of routine. It is not aimed at women who already have symptoms.

If you have found something that worries you, don't wait to be offered screening – see your GP. He or she will decide whether or not you need to be referred for further investigations or treatment.

Read more about the symptoms of breast cancer.

My sister lives abroad and she gets more frequent breast screening. Why doesn't this happen in the UK?

A large research trial in 2002 concluded that the NHS Wales Breast Screening Programme has got the interval between screening and invitations about right at three years, compared with more frequent screening. The trial was organised through the United Kingdom Coordinating Committee on Cancer Research (UKCCCR) and was supported by the Medical Research Council, Cancer Research UK and the Department of Health.

Here are the results from the UKCCCR Randomised Trial (PDF, 186kb) from the European Journal of Cancer, 2002.

I'm worried that breast screening will hurt because of the size of my breasts...

Don't worry. The mammography practitioners are used to screening women of all sizes and will do their best to minimise any discomfort.

During the mammogram each breast is placed in turn on the X-ray machine and gently but firmly compressed with a clear plate. The compression only lasts a few seconds and doesn't cause any harm. It's needed to keep the breast still and to get the clearest picture with the lowest amount of radiation possible.

Research has shown that for most women it's less painful than having a blood test and compares with having blood pressure measured. For women with very large breasts, additional pictures are sometimes needed to ensure that all the breast tissue is included.

Can I walk into the mobile breast screening unit and request a mammogram?

No – the NHS Wales Breast Screening Programme doesn't operate on a walk-in basis. It invites women in the target age group (50 to 70) for routine breast screening every three years.

If you have found something that worries you or are concerned about your breast health, don't wait for your routine screening appointment. You should contact your GP.

Why does breast screening stop at 70?

It doesn't. Although women over 70 are not routinely invited for breast screening, they are encouraged to call their local breast screening unit to request breast screening every three years.

We produce cards to help them remember, which are handed out at their last routine breast screening appointment.

Can women with a physical disability be screened?

Mammography is a procedure that is technically difficult and that requires a high degree of cooperation between the mammography practitioner and the woman.

The woman has to be carefully positioned on the X-ray machine, and must be able to hold the position for several seconds. This may not be possible for women with limited mobility in their upper bodies or who are unable to support their upper bodies unaided.

If a woman has a physical disability or is a wheelchair user, the breast screening unit should advise on whether breast screening is technically possible, and where would be the most appropriate place for her to be screened. This will usually be at a static unit.

If a mammogram is not technically possible, the woman should still remain in the call and recall programme, as any increased mobility at a future date may make screening easier.

If a woman cannot be screened, she should be advised on breast awareness.

I am a carer, looking after someone who lacks the mental capacity to make their own decisions about screening. They have been invited for breast screening. How should I deal with their invitation?

If the person you care for is unable to make their own decisions about screening, then you, as their carer, should make what is called a 'best interests' decision on their behalf, in the same way as you may be making other decisions about their care and treatment.

You will need to weigh up the benefits of screening, the possible harm to them and what you think the person would have wanted to do themselves. Whether you are a paid carer, or an unpaid carer, family member or close friend, the process is the same.

Some people may have fluctuating mental capacity – in which case, the decision about screening should be delayed until the individual is able to decide for themselves.

If you do need to make a decision on someone else's behalf, consider what is involved in the screening process (including any further diagnostic tests that may be needed if the person receives an abnormal screening result). You may find it helpful to speak to their GP to discuss, for example, the person's risk of developing the cancer in question and how screening may affect them.

You must also consider what you think the person themselves would want. For example, did they used to go to screening, or express an opinion about it? Did they express more general views about their health and whether they would want to know if they had a disease or condition? Or did they refuse screening in the past?

Paid carers in particular should get advice from family members or friends about the person's views. If, after all this, you consider that screening is in the best interests of the person you care for, then you are within your rights to help that person to be screened. You should feel confident that if someone asks you, you will be able to explain the reasons for the best interests decision that you have made – either for, or against, screening.

To help someone with limited capacity to understand the screening process, you may find the picture leaflet An easy guide to breast screening helpful.

I'm in the process of changing from a man to a woman. I'm over 50. Am I entitled to breast screening?

Individuals who are undergoing male to female gender reassignment may be screened as a self-referral at the request of their GP. If you have a symptom, you should see your GP in the usual way.

I am changing from a woman to a man. Will I still be offered breast screening?

Individuals who are undergoing female to male gender reassignment will continue to be invited for breast screening as long as they are registered as a woman, unless they ask to be removed from the programme or have had both breasts removed.

What happens to my mammograms after screening?

The NHS Wales Breast Screening programme will keep your mammograms for at least eight years. These are saved securely.

The screening programme regularly checks records to make sure the service is as good as possible. Staff in other parts of the health service may need to see your records for this, but your records will only be shared with people who need to see them.

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 01/02/2023 10:57:20