Screening mammograms can detect breast cancer before it can be felt, often when it is smaller and easier to treat. Early detection improves treatment options and outcomes and helps reduce deaths from breast cancer.
Women who get screened are:
- less likely to die from breast cancer
- less likely to need more extensive surgery, like mastectomy
- less likely to have breast cancer spread to lymph nodes
- less likely to need chemotherapy
The most lives are saved by starting mammograms at age 40. Most provinces and territories now allow women at average risk to self-refer for a screening mammogram starting at age 40. If your province/territory does not offer self-referral at 40, you can request a requisition from your healthcare provider at age 40.
How often you should be screened depends on your age, personal risk factors, breast density, and your provincial or territorial screening program. Some women benefit from annual screening: women with a family history, women with Category D density and women with breast cancer. Women in their 40s can go annually in YT, NS, NL, and PEI. Women with Category D are recalled annually in seven jurisdictions. Women aged 50-74 at average risk are invited every 2 years.
According to Canadian breast screening experts, women over age 74 should continue to screen every 1-2 years with mammography as long as they are in good health, with a life expectancy of at least 7 years, and as long as they are willing to have treatment if a cancer is found. Treatment is often modified for older women. Women 75 years and up receive the same benefits of early detection from screening as younger women: more lives saved through less invasive treatment.
In these provinces, women 75 years and over need a requisition: PEI, AB, NB, ON, QC, and NWT but in the other jurisdictions they can continue to self-refer.
- The incidence of breast cancer increases at age 40
- 1 in 6 breast cancers are found in women in their 40s
- Half of fatal cancers are diagnosed by age 49
- Women who screen in the 40s are 44% less likely to die from breast cancer than women who do not have mammograms
Visit our My Province page to learn about eligibility, self-referral, and booking information for your province or territory.
Getting Started
Breast screening saves lives by finding breast cancer early, often before it can be felt or cause symptoms. This section explains when to start screening, how often to be screened, and why regular mammograms are one of the most effective tools for reducing deaths from breast cancer.
Understanding Mammograms
Mammograms are the foundation of breast cancer screening, but many women have questions about what to expect and what the results mean. Learn how mammograms work, their benefits and limitations, and why they remain the most important screening test for most women.
A mammogram is a low-dose X-ray of the breast that can show breast cancer. Mammograms can detect cancer early, when it is most treatable and long before it can be felt. This improves the odds of survival and can help avoid more extensive treatment. However, mammography is not a perfect test, as discussed in the section below on dense breasts.
A specially trained technologist will perform your mammogram. To get a high-quality picture, your breast must be compressed. The technologist will place your breast on the machine. The plastic upper plate is lowered to compress your breast while the technologist takes a picture. Compression is used to spread out the tissue, so radiologists can see better, and that includes seeing cancers. The actual breast compression only lasts about 10 seconds. A top-to-bottom image and a side view of each breast are taken for a screening mammogram. All mammography machines have a release switch, so the compression releases as soon as the exposure is made.
The most common complaint about mammography is the uncomfortable feeling when the breast is temporarily compressed (10 seconds). To alleviate some of the discomfort, these tips can be considered:
- Premenopausal woman can schedule the exam 5 to ten days after the beginning of their period when the breasts are less tender.
- Consider taking ibuprofen an hour before.
- Tell the technologist about your previous experience.
This video shows how compression makes a difference.
Mammograms can find cancer early: Mammograms can find cancerous tumours 2-3 years before they can be felt. Finding breast cancer early can increase survival and also reduce the need for harsher treatments like chemotherapy and mastectomy.
A mammogram can save your life: Multiple studies have found that routine screening from age 40-74 substantially reduces deaths from breast cancer. Current evidence shows women aged 40-49 who have mammograms are 44% less likely to die of breast cancer. Women aged 50-74 are 40% less likely to die of breast cancer.
Mammograms help you find out your breast density: It’s important to know if you have dense breasts, which can increase your risk. Your breast density can only be assessed by
the radiologist from looking at your mammogram.
Current evidence shows that the benefits of mammograms outweigh the limitations for women aged 40-74.
Mammograms may lead to more tests, which can create anxiety.
You may be told that mammograms can result in “false positives”, but a better term would be “false alarm.” Any time the mammogram shows something unclear that has any possibility of being cancer, you will be recalled for extra images to see the area more clearly. About 10% of women are recalled, and over 95% of these women do not have cancer. Waiting for the extra tests and the results can be stressful. However, evidence shows that the anxiety is short-lived and does not harm women psychologically in the long term.
Over detection/Over diagnosis
You may be told that there is a theoretical possibility that you could be diagnosed and treated for a cancer that would never threaten your life, even if it was not treated. It’s not that there are “harmless cancers,” it’s just that some cancers are more aggressive, and some grow so slowly that you might die of something else (another cancer, a heart attack, etc.) before
the breast cancer becomes deadly. Since doctors can’t predict perfectly which cancers can be left untreated, all cancers are treated. But there is ongoing research to determine if some cancers can be treated less aggressively.
Not all breast cancers can be detected by mammograms.
Cancer may not be visible on the mammogram or may develop between two mammograms. A woman’s age, the location of the
cancer, and a woman’s breast density can make cancers more or less difficult to see.
Mammograms use low doses of radiation
A mammogram is an X-ray and uses a low dose of radiation, slightly higher than a chest X-ray. The risk of breast cancer due to radiation from a mammogram is very low, and probably negligible after age 40. The benefit of early diagnosis and treatment for breast cancer far outweighs the risk of the small amount of radiation received during a mammogram.
A screening mammogram is used to look for breast cancer in a woman who has no signs or symptoms of breast cancer. Screening mammograms do not prevent breast cancer. Their purpose is to detect breast cancer as early as possible and before it is large enough to be felt or cause symptoms.
A diagnostic mammogram is used for women with symptoms. Diagnostic mammography is also performed for women with an abnormal screening mammogram.
No. There is no evidence that breast compression during a mammogram causes cancer to spread. Compression is necessary to spread out the breast tissue, producing clearer images while using the lowest possible radiation dose. Compression lasts only a few seconds.
Yes. Mammography uses a very low dose of radiation, only slightly higher than a chest X-ray. The risk of breast cancer due to radiation from a mammogram is very low, and probably negligible after age 40. The benefit of early diagnosis and treatment for breast cancer far outweighs the risk of the small amount of radiation received during a mammogram. Read our blog post on radiation.
No. Mammograms are the standard screening test for most women, but they do not detect every breast cancer. If you have dense breasts, a normal mammogram result may not be accurate. Cancers are missed ~30% of the time in Category C density and ~40% of the time in Category D. If you notice a new breast symptom, it should always be evaluated, even if your mammogram was normal.
Breast density describes the proportion of fibroglandular tissue compared with fatty tissue seen on a mammogram. Breast density is divided into four categories: A, B, C, D. C and D are considered to be dense breasts. Dense breasts are common, increase the risk of breast cancer, and can make cancer more difficult to detect on a mammogram. Learn more on our Dense Breasts page.
Knowing your breast density is an important part of understanding your breast cancer risk and making informed decisions about screening. It’s important to know if you have dense breasts. Both increase the risk of breast cancer and make it more difficult to detect on a mammogram. Learn more on our Dense Breasts page.
The only way to determine your breast density is by having a mammogram. Breast density cannot be determined by how your breasts look or feel or by a physical examination. After your mammogram, ask for your breast density category if it is not included with your results.
Yes. Breast density often decreases with age, particularly after menopause, but not for everyone. Some women continue to have dense breasts throughout their lives. Because breast density can change, it is important to know your breast density after each screening mammogram.
Yes, supplemental screening with ultrasound or MRI is essential. Mammograms are not enough. Discuss your breast density, your family history, and your overall risk of breast cancer using the Tyrer-Cuzick risk calculator and determine which type of additional screening is best.
Breast Density
Breast density is an important part of breast health that every woman should know. Dense breasts are common, increase the risk of breast cancer, and can make cancers harder to detect on a mammogram. This section explains what breast density means and how it can affect your screening plan.
Your Breast Cancer Risk
No two women have the same risk of developing breast cancer. Understanding your personal risk—including your breast density, family history, and overall risk assessment—can help you and your healthcare provider choose the screening approach that is right for you.
Mammography reduces mortality from breast cancer, but it is an imperfect screening tool for women with dense breasts because it can miss cancerous tumors in dense breasts.
Mammograms can miss cancer about 40% of the time in the densest breasts. Therefore, women with dense breasts might want to consider additional screening with their mammogram. Ultrasound or MRI, when combined with mammography, significantly improves the rate of cancer detection in women with dense breasts.
In Canada, additional screening is not easily accessed. You may need to advocate for yourself.
Many factors influence breast cancer risk, including age, family history, inherited gene mutations, breast density, previous breast cancer, prior chest radiation, and certain lifestyle factors. Knowing your personal risk can help guide screening decisions.
A breast cancer risk assessment estimates your likelihood of developing breast cancer based on factors such as age, family history, breast density, reproductive history, and, in some cases, genetic information. Knowing your risk can help determine the most appropriate screening plan. The risk calculator most used in Canada is the Tyrer-Cuzick calculator.
To make informed screening decisions, every woman should know:
- Her breast density.
- Her family history of breast cancer.
- Her overall breast cancer risk (such as a Tyrer-Cuzick risk assessment).
No. Most women (85%) diagnosed with breast cancer do not have a family history of the disease. Family history is only one of many factors that influence risk.
Please check with your provincial screening program for its policies regarding high-risk women. In Ontario, women deemed as high risk must meet the following criteria, but your province may have different criteria.
- Have a gene mutation that increases their risk for breast cancer (e.g., BRCA1, BRCA2, TP53, PTEN, CDH1)
- Have a first-degree relative (parent, brother, sister, or child) who has a gene mutation
- Have been assessed by a genetics clinic as having a 25% or greater lifetime risk of breast cancer based on personal family history
- Have had radiation therapy to the chest to treat another cancer or condition (e.g., Hodgkin lymphoma) before age 30 and at least 8 years ago
Genetic testing is not recommended for everyone. It is generally offered to people with a strong personal or family history of breast, ovarian, pancreatic, or prostate cancer, or those who meet specific criteria. It is also recommended for women who score over 25% on the Tyrer- Cuzick risk assessment. Talk to your healthcare provider if you think you may qualify for genetic counselling and testing.
Yes. Not all breast cancers cause a lump. Breast cancer can also present as nipple discharge, skin dimpling, thickening of the breast or underarm, nipple inversion, redness, swelling, or changes in breast size or shape. Some breast cancers cause no symptoms at all and are found only on screening mammograms.
The most common symptom of breast cancer is a new breast lump or thickening, but breast cancer does not always cause a lump.
Other symptoms can include:
- A new lump in the breast or underarm (armpit)
- Thickening or swelling of part of the breast
- Changes in the size or shape of the breast
- Skin dimpling or puckering
- Redness, warmth, or thickened skin
- A nipple that turns inward (new nipple inversion)
- Bloody or spontaneous nipple discharge
- Persistent pain in one area of the breast
- Swelling in the underarm or around the collarbone
If you notice any of these symptoms, do not wait for your next screening mammogram. See your healthcare provider promptly and request diagnostic breast imaging. Remember, a normal screening mammogram does not rule out breast cancer, particularly if you have dense breasts. Check out KnowYourLemons.org for a great graphic of the symptoms.
Do not wait for your next screening mammogram. If you notice a new lump, nipple discharge, skin changes, persistent pain in one area, or any other unusual breast change, see your healthcare provider promptly and request imaging.
Yes. Screening mammograms are designed for women who have no signs or symptoms of breast cancer. The goal is to find breast cancer before it can be felt or causes symptoms, when it is more likely to be treated successfully. If you have a lump, nipple discharge, skin changes, or another new breast symptom, you should not wait. See your healthcare provider promptly and request diagnostic breast imaging.
Breast pain by itself is not usually a sign of breast cancer and is very common, especially before menopause. However, that said, some women with breast cancer do report having pain. If the pain is persistent, occurs in one specific area, or is accompanied by a lump, skin changes, or nipple discharge, you should see your healthcare provider for assessment. Do not ignore persistent or concerning symptoms.
Yes. Being familiar with how your breasts normally look and feel can help you recognize changes that should be assessed promptly.
Symptoms
Screening mammograms are for women without symptoms, but it is equally important to recognize when a breast change needs prompt medical attention. Learn the signs and symptoms of breast cancer and when to seek diagnostic breast imaging, even if you have recently had a normal mammogram.
Other Common Questions
Breast screening doesn't always fit neatly into one category. Here you'll find answers to common questions about screening during pregnancy and breastfeeding, breast implants, breast cancer in men and younger women, transgender screening, and other important topics.
Yes. Although the risk of breast cancer increases with age, the incidence in younger women is rising globally. Breast cancer can occur at almost any adult age.
Yes. Although breast cancer is much less common in men than in women, it can occur. Men who notice a lump or any other breast change should seek medical assessment promptly. Men who have a mother, sister, or daughter with breast cancer are at increased risk
Yes. Mammograms can be performed during pregnancy or while breastfeeding when they are medically appropriate. The amount of radiation used during a mammogram is very low, and the fetus is not in the direct path of the X-ray beam. If you are pregnant or think you may be pregnant, tell the imaging facility before your appointment.
Breastfeeding is not a reason to delay a mammogram. In fact, breast cancer can occur during pregnancy and breastfeeding, so any new breast lump or other concerning change should be assessed promptly. Emptying your breasts by breastfeeding or pumping just before your mammogram may make the examination more comfortable and can improve image quality.
Talk with your healthcare provider about the most appropriate breast imaging for your individual situation, particularly if you have symptoms or are at increased risk of breast cancer.
Women with breast implants still need regular mammograms. In most provinces, women with implants require a requisition for a diagnostic mammogram. Only in Alberta and Quebec are women with implants included in the screening program and can self-refer after age 50.
There are four images taken of each breast, two including the implant and two with the implant pushed back out of the way.
The “usual” views (the compression vertically, and the compression angled side-to-side) are obtained on each side. These include the implant and allow inclusion of tissue as far back as possible in each image. In addition, similar angles are used, but with the implant pushed back so only the breast tissue is included in the images. These allow better compression and visualization of the breast tissue, but can’t include as much of the tissue at the back of the breast.
Current evidence shows that females transitioning to male who do not undergo mastectomies maintain their previous risk for breast cancer. Males transitioning to female are at increased risk for breast cancer due to hormone use. The American College of Radiology recommends annual screening starting at age 40 in male-to-female patients who have used hormones for 5 years or more, and for female-to-male patients who have not had mastectomy. Please check your provincial screening program for policies.
One size does not fit all when it comes to screening. Canadian breast screening guidelines do not recognize that minority women are underserved by screening starting at age 50. Here are the latest statistics:
- A Black woman in her 40s faces a breast cancer mortality rate that is 40% higher compared to White women of the same age group
- First Nations and Métis women in their 60s face mortality rates 20% to 50% higher than White women of the same age group, respectively
- The peak age of breast cancer diagnosis was 65 for White women, compared to ages 42-60 for women of other race and ethnicity groups
- About 1/3 of breast cancer cases were diagnosed before age 50 in Arab, Inuit, Korean, West Asian and multiethnic women compared to 16% in White women.