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A mammogram is an X-ray of the breast that can find abnormal changes in the breast, even when they may be too small to feel or see.

Safety of Mammography

Mammography uses a low dose of radiation. The benefits of screening and finding cancer early are more important than potential harm from the X-ray.

Effectiveness of Mammograms

  • Getting screened regularly with mammography is important because it can find cancer early when it is less likely to have spread to other parts of the body. Treatment may also have a better chance of working when breast cancer is found early.
  • Research shows that women ages 50 to 74 who get screened regularly with mammography can lower their chance of dying from breast cancer.
  • Mammography is not a perfect test and may miss some breast cancers. This is called a “false-negative” result. In addition, some cancers may grow in the time between screens. This is why regular screening is important.
  • Mammograms are sometimes abnormal, but when a person has more tests (e.g., biopsies), the tests might show that they have no cancer. This is called a “false-positive” result.
  • Some breast cancers found through screening may never harm a person during their lifetime. This means some people may have surgery or treatment for a breast cancer that would have never been life-threatening. This is called “over-diagnosis.”
  • Some cancers found at screening cannot be treated successfully.

Talk to your family doctor or nurse practitioner for more information about the benefits and limitations of screening with mammography.

Getting Ready for a Mammogram

You should book your mammogram for a time when your breasts are not tender. Your breasts may be tender:

  • the week before and after your period
  • if you have drinks with caffeine (like coffee, tea or other drinks high in caffeine)

Some experts say that having less caffeine for 2 weeks before your mammogram can help make your breasts less tender.

On the day of your mammogram:

  • wear a 2-piece outfit (like a top and pants) because you will be asked to take off your top
  • do not use deodorants, antiperspirants, body lotions or talcum powders because they can affect the accuracy of the mammogram

What Happens During a Mammogram

If you are planning to have a mammogram to check for breast cancer, you may be wondering what it will be like.

  • A medical radiation technologist (someone who is trained to take mammograms) will place your breast on the mammography machine.
  • A plastic plate will move down slowly to press the breast and hold it in place.
  • There will be some pressure for a few seconds on the breast, much like a tight blood pressure cuff. This pressure does not harm your breast tissue. The person taking the mammogram is trained to make sure the experience is as comfortable as possible and will be able to adjust the pressure if needed.
  • Mammograms are taken of each breast from 2 different angles.
  • The appointment usually takes about 15 minutes.

Getting Your Results – What Happens Next

Normal Results

If your mammography results are normal, the Ontario Breast Screening Program will notify your family doctor or nurse practitioner. The program will also send you a letter with your results and when to get screened again.

Abnormal Results

If you have an abnormal screening result, your Ontario Breast Screening Program location will notify your family doctor or nurse practitioner and may also help to schedule a timely follow-up appointment.

If you have an abnormal mammogram and do not have a family doctor or nurse practitioner, your screening location will assign you to a doctor or nurse practitioner who will follow you to diagnosis.

Most people with an abnormal mammogram do not have breast cancer. More tests are needed after an abnormal mammogram to find out whether a person has cancer. These tests may include more mammography, breast ultrasound, breast magnetic resonance imaging and/or biopsies.

If you are diagnosed with breast cancer, you will be referred to a specialist for further care and management.

For more information about breast cancer screening, eligibility and booking a screening appointment, see Screening for Breast Cancer.