Diagnostic mammography

Expert reviewer, Miss Rachel Bright-Thomas, Consultant Breast Surgeon.
Next review due May 2019

A mammogram is an X-ray of your breasts that checks for changes that may be related to cancer. You can have a mammogram as part of a screening programme for breast cancer, or to help diagnose cancer if you’ve had breast symptoms.

This information relates to mammograms used to diagnose breast cancer in women who have had symptoms. If you’re having a mammogram as part of a screening programme, see our breast screening topic for more information.

Why do you need a diagnostic mammogram?

Your doctor may advise you to have a mammogram if you have breast symptoms that could be a sign of cancer. These might be an unexplained lump in your breast or armpit, for example, or discharge from your nipple.

You’ll usually be referred to a breast assessment unit in a local hospital for your mammogram. You’ll also see a specialist doctor at the unit for an examination, and you may also be offered an ultrasound scan too. If you’re under 40 or you’re pregnant or breastfeeding, you may be offered an ultrasound scan instead of a mammogram. Younger women have a lower risk of breast cancer and also tend to have breast tissue that is more dense (solid). This means that a mammogram is more likely to miss any changes that could be a sign of cancer. Doctors can also find it more difficult to read the mammograms correctly.

If your doctor finds anything in your examination or scans, you’ll also be offered a biopsy. This is when a sample of tissue is taken from your breast for testing.

Preparing for your mammogram

Your mammogram will usually be carried out by a mammography practitioner (or mammographer) in the breast assessment unit. These are women who are specially trained to carry out mammograms. 

You may find it helpful to take a friend or relative with you when you go to the breast assessment clinic, but they probably won’t be able to come into the X-ray room with you.

Don’t use deodorant or talcum powder on the day of your mammogram, as these could affect the quality of the X-ray image. 

If you’re pregnant or think you may be, let your mammographer know. When you have a mammogram, you receive a very low dose of radiation, which could affect your unborn baby. You may be given an ultrasound scan rather than a mammogram. Or, if you have the mammogram, you’ll be given a lead apron to wear. A lead apron is a shield that protects your baby from any radiation.

If you have breast implants, tell your mammographer. X-rays can’t pass through a breast implant to the tissue behind it. This means that some of your breast tissue can be hidden. Your mammographer may need to change the way they take the image or take extra images, to make sure they can see as much breast tissue as possible. Mammograms can’t check on the health of your implants themselves, so you’ll need separate tests for this if you have any concerns.

What happens during a mammogram?

You’ll be asked to undress to your waist. The mammographer will help you to position each breast on the X-ray machine. Once you’re ready, a flat, plastic plate will move down to gently compress your breast. This helps to keep your breasts still while the X-rays are taken, and also makes the images clearer. Your breasts will be X-rayed one at a time, and normally at least two images of your breasts will be taken from different angles. The images are usually digitally recorded and can be displayed on a computer.

You may well find the procedure uncomfortable, and some women find it painful – but it will only last for a few seconds, and it won’t harm your breasts.

You’ll be able to get dressed straight after your mammogram and go home when you’ve finished your consultation with the doctor.

Getting the results of your mammogram

Your doctor may be able to give you some idea of whether or not they’ve found anything in your mammogram on the day of your test. Normally though, your doctor will need the results of all the tests you’ve had before they can make an accurate diagnosis. You’ll usually be asked to come back for an appointment to receive your results. Or sometimes, you may be able to get your results over the phone or by letter. You should usually get your results within five days of having your test.

If your mammogram is negative (it doesn’t find anything), you’ll be discharged from the clinic. If your symptoms continue or you develop any new symptoms, you should see your GP again. They may refer you back to the clinic. 

Sometimes, you may be asked to have other imaging tests, such as an ultrasound or MRI. This may be if results from initial tests aren’t clear enough to confirm cancer. Ultrasound scans are also good at diagnosing other non-cancerous problems, such as cysts. If you’re found to have another condition such as a cyst, your doctor will explain what this means and if you need any further tests or treatment.

If your test results do show you have breast cancer, it can come as a huge shock because it’s a lot to take in. You’ll be allocated a specialist breast cancer nurse, who will be able to support you through your diagnosis and treatment.

What are the risks?

When you have a mammogram, you’re exposed to small amounts of radiation from the X-rays. But the amount of radiation is very small and shouldn’t be harmful. The benefits of diagnosing breast cancer with a mammogram allow you to get the treatment you need, and outweigh any risks of the procedure.

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Related information

    • Stedman’s Medical Dictionary. Lippincott Williams & Wilkins., accessed 27 April 2016
    • Early and locally advanced breast cancer: diagnosis and treatment. National Institute for Health and Clinical Excellence (NICE), February 2009.
    • Map of Medicine. Breast cancer. International View. London: Map of Medicine; 2015 (Issue 5)
    • Mammogram and other tests. Breast Cancer Care., last reviewed January 2014
    • Mammography. PatientPlus., last checked 23 January 2014
    • Pregnancy and breast cancer. Green-top guidelines 12. Royal College of Obstetricians and Gynaecologists, March 2011.
    • Common questions about breast screening., reviewed 31 August 2014
    • Breast cancer. Oxford handbook of oncology (online). Oxford Medicine Online., published September 2015
    • Primary invasive breast cancer. BMJ Best Practice., last updated 25 April 2016
  • Reviewed by Pippa Coulter, Specialist Health Editor, Bupa Health Content Team, May 2016
    Expert reviewer, Miss Rachel Bright-Thomas, Consultant Breast Surgeon
    Next review due May 2019

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