About 1 in 8 women in the UK are diagnosed with breast cancer during their lifetime. If it's detected early, treatment is more successful and there's a good chance of recovery.
Breast screening aims to find breast cancers early. It uses an X-ray test called a mammogram that can spot cancers when they're too small to see or feel.
But there are some risks of breast cancer screening that you should be aware of.
As the likelihood of getting breast cancer increases with age, all women aged from 50 to their 71st birthday who are registered with a GP are automatically invited for breast cancer screening every 3 years.
In the meantime, if you're worried about breast cancer symptoms, such as a lump or an area of thickened tissue in a breast, or you notice that your breasts look or feel different from what's normal for you, do not wait to be offered screening. See a GP.
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.
The main risk is that breast screening sometimes picks up cancers that may not have caused any symptoms or become life threatening.
You may end up having unnecessary extra tests and treatment.
Breast screening is offered to women aged 50 to their 71st birthday in England.
But currently there's a trial to examine the effectiveness of offering some women 1 extra screen between the ages of 47 and 49, and 1 between the ages of 71 and 73.
You'll first be invited for screening within 3 years of your 50th birthday, but in some areas you'll be invited from the age of 47 as part of the age extension trial.
You may be eligible for breast screening before the age of 50 if you have a very high risk of developing breast cancer.
If you're 71 or over, you'll stop receiving screening invitations.
You can still have screening once you're 71 or over if you want to, and can arrange an appointment by contacting your local screening unit.
Breast screening involves having an X-ray (mammogram) at a special clinic or mobile breast screening unit. This is done by a female health practitioner.
Your breasts will be X-rayed 1 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.
After your breasts have been X-rayed, the mammogram will be checked for any abnormalities.
The results of the mammogram will be sent to you and your GP no later than 2 weeks after your appointment.
After screening, about 1 in 25 women will be called back for further assessment.
Being called back does not 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.
For more information, the Breast Cancer Screening Programme has guides about:
The GOV.UK website also has breast cancer screening leaflets in other languages.