Frequently Asked Questions
What Is Breast Density?
WHAT ARE DENSE BREASTS? HOW COMMON ARE THEY?
All breasts contain a mix of 3 types of tissue: connective, glandular and fatty tissue. Dense breasts have more connective and glandular tissue than fatty tissue.
Dense breasts are very common and normal. About 43% of women over the age of 40 have dense breasts: that is about 3 million women in Canada. The majority of women do not know if they have dense breasts.
HOW IS BREAST DENSITY DETERMINED?
Breast density is determined by the radiologist who reads your mammogram. It is NOT determined by the size or firmness of your breasts. You cannot tell density by look or feel. Dense breasts are not the same as lumpy breasts.
WHAT ARE THE CATEGORIES USED TO DESCRIBE BREAST DENSITY IN CANADA?
The categories used to describe your density depend on where you live (see page: Density by Province).
UNDER 25% dense tissue/Category A: Almost entirely fatty: the breasts have little fibrous and glandular tissue and are mostly fat. A mammogram would likely detect an abnormality.
25%-50% dense tissue/Category B: Scattered areas of fibroglandular density: the breasts have scattered areas of fibrous and glandular tissue, but also quite a bit of fat.
51-74% dense tissue/Category C: Heterogeneously dense: the breasts have consistently distributed areas of fibrous and glandular tissue, making it hard for small masses to be detected by mammogram.
75% and above dense tissue/ Category D: Extremely dense breasts: the breasts have a lot of fibrous and glandular tissue, making it even harder for a cancerous tumor to be detected by mammogram.
** ABOVE 50% / CATEGORY C and D ARE CONSIDERED DENSE BREASTS. Dense breast tissue may obscure small tumors and make a mammogram less accurate.
HOW MANY WOMEN HAVE "FATTY" BREASTS VS. "DENSE" BREASTS?
Only 10% of women have the lowest category of density known as ‘Fatty’ breasts and only 10% have the highest category ‘Extremely Dense.’ An additional 40% of women fall in the other category considered to be dense breasts: heterogeneously dense breasts.The risks associated wiht dense breasts increase as the density increases.
WILL MY BREAST DENSITY CHANGE?
Dense breasts are more common in younger, premenopausal women. As women get older, their breasts usually become less dense, but not always.
56% of women in their 40s have dense breasts.
37% of women in their 50s have dense breasts.
27% of women in their 60s have dense breasts.
WHAT IF I DO NOT HAVE DENSE BREASTS?
Have a regular mammogram. Other factors may still place you at increased risk. Talk to your doctor and discuss your history. Women considered to be at high risk will likely be sent for an MRI, as well as a mammogram. Screening saves lives.
Why Does My Breast Density Matter?
HOW DOES MY BREAST DENSITY AFFECT MY MAMMOGRAM? BOTH 2D AND 3D?
Dense breasts make it harder for doctors to spot cancer on 2D digital mammograms because BOTH CANCER AND DENSE TISSUE APPEAR WHITE on mammograms. A camouflage effect is created. Fatty tissue, on the other hand, is black on a mammogram and the contrast makes cancer easier to detect. Mammograms are 98% accurate in women with fatty breasts but may be less than 50% accurate in women with dense breasts.
Kolb, T., Lichy, J., & Newhouse, J. (2002). Comparison of the performance of screening mammography, physical examination, and breast US and evaluation of factors that influence them: an analysis of 27,825 patient evaluations. Radiology. (225):165–17. http://www.surgery.usc.edu/uppergi-general/downloads/readinglist/2002-10-comparison-of-performance-screening-mammography.pdf
WHAT ABOUT 3D MAMMOGRAM (TOMOSYNTHESIS)?
Tomosynthesis (3D mammogram) is becoming available in some provinces. It increases the detection of invasive cancer by an additional 1-2 cancers per 1000 women. However, its effectiveness declines as density increases. Tomosynthesis does not detect as many cancers in women with the densest breasts (women with over 75% dense tissue/ Extremely Dense Breasts).
Supplementary ultrasound detects more cancers in dense breasts than Tomosynthesis, The evidence for the past 40 years shows that mammography is not enough for women with dense breasts.
pictures courtesy of Dr. Wendi Berg and densebreast-info.org
HOW DOES MY BREAST DENSITY AFFECT MY CANCER RISK?
This is not to scare you, but you need to know…the more dense the breast, the higher the risk of breast cancer.
Women with the highest level of density (Category D-75% and over dense tissue) are 4-6 times more likely to get cancer than women with the lowest (Category A- <25 % dense tissue).
As well, since mammograms detect about 50% of cancers in dense breasts vs. 97% in fatty breasts, cancer found in dense breasts is usually detected at a later stage, possibly making prognosis worse.
Breaking news: A recent study from The University of California. San Francisco, showed that “breast density may be the most important gauge of breast cancer risk, eclipsing family history of the disease and other risk factors.”
Boyd, N., Guo, H., Martin, L., Sun, L., Stone, J., Fishel, E., Jong, R., Hislop, G., Chiarelli, A., Minkin, S., and Yaffe, M. (2007, Jan.). Mammographic density and the risk and detection of breast cancer. New England Journal of Medicine, 356:227-236. http://www.nejm.org/doi/full/10.1056/NEJMoa062790#t=article
Engmann N, Golmakani M, Miglioretti D, Sprague B, Kerlikowske K, for the Breast Cancer Surveillance Consortium. (2017, Feb 2.)Population-Attributable Risk Proportion of Clinical Risk Factors for Breast Cancer. JAMA Oncol. http://jamanetwork.com/journals/jamaoncology/article-abstract/2599991
Why Does It Matter What Province I Live In?
HOW CAN I FIND OUT MY DENSITY IN MY PROVINCE?
There is wide variation in density reporting following a screening mammogram in a provincial screening program.
- In some provinces, you can just ask your doctor what the mammogram states about your breast density and the information may be available. Or it may not.
- In some provinces, your doctor has not been told.
- In some provinces, there is no way to get complete density information.
If you live in BC: Your doctor is not told your density. You can easily send in this “Request for Access to Records” form to find out: http://bit.ly/2r1gtcl (See Density Reporting Section for more info).
If you live in MB or NS: Your doctor is not told your density. It is worthwhile to send in a request for information form. However, you can only find out your density if you have been assessed as Category D:75% and over dense tissue. You cannot find out if you are in Category C: 50-75% , which is also considered Dense Breasts because this information is not recorded (See Density Reporting Section for form).
If you live in SK and NL: You and your doctor are only notified if you are assessed as having 75% and above dense breast tissue. There is no way to find out if you are in the 50-75% density category which is also considered as dense breasts (See Density Reporting Section).
If you live in the other provinces: your family doctor may or may not have the information. It depends if the radiologist who reads your mammogram has conveyed the information. You need to ask your doctor what your mammogram report says.
**The information applies to a screening mammogram, not a diagnostic mammogram. It applies only to women being screened under their provincial breast screening programs.
|Density is NOT reported to family doctor||Women with 75% and over dense tissue are asked to return for a mammogram in 1 year instead of 2||Density is sometimes but not always described in report to family doctor|
|Nova Scotia||Ontario||NWT ( under 75% or over 75%)
|Saskatchewan (only if patient has over 75% density)||NWT||New Brunswick|
|Newfoundland (only if patient has over 75% density)||New Brunswick (depends on zone)
|Nova Scotia (sometimes)
What Should I Do If I Have Dense Breasts?
WHAT SHOULD I DISCUSS WITH MY DOCTOR? HOW DO I ADVOCATE FOR SCREENING?
Discuss your density category and any other risk factors such as genetics, family history, previous biopsies, etc. so that your overall cancer risk is understood.
If you have dense breasts, talk to your doctor about having added screening such as ultrasound because a ‘NORMAL’ mammogram result may not be accurate. Dense tissue can mask cancer. Ultrasound finds additional cancers. You are the best advocate for your health and you may have to advocate for additional testing.
HOW TO ADVOCATE FOR ADDITIONAL SCREENING
It is NOT Canadian protocol to order ultrasound for women with dense breasts unless an abnormality has been detected by mammogram or clinical examination. Yet, we know early detection is key.
If you want added screening, advocate for yourself and let your doctor know you are aware of the following risks:
- The increased cancer risk associated with dense breasts. Dense breasts are an independent risk factor. Dense breasts are a more significant risk factor than family history.
- The unreliability of mammography for dense breasts because of dense tissue’s camouflaging effect
- The high level of interval cancers for women with dense breasts- cancers detected in between screenings
- The proven ability of ultrasound and MRI to detect additional cancerous tumours missed by mammogram
In most cases, when extra screening is done, women are NOT found to have breast cancer.
WHY IS ULTRASOUND BENEFICIAL FOR WOMEN WITH DENSE BREASTS?
Ultrasound can detect a small cancer in an early stage before it spreads to lymph nodes.
In women with dense breasts, studies show that for every 1000 women screened, ultrasound finds another 3-4 cancers that were not seen on mammogram.
Several large studies have shown that supplementing mammograms with Ultrasound can increase detection up to 97% in women with dense breasts.
Berg, W, Blume, J., Cormack, J. et al. (2008). Combined screening with ultrasound and mammography vs. mammography alone in women at elevated risk of breast cancer. JAMA, 299: 2151-63. http://www.ncbi.nlm.nih.gov/pubmed/18477782
IF ULTRASOUNDS ARE BENEFICIAL, WHY ARE THEY NOT PROTOCOL FOR WOMEN WITH DENSE BREASTS?
Ultrasound is used when an abnormality is detected by mammogram or clinical exam. It is not used routinely for screening because it is a sensitive test and can sometimes result in false positives – an abnormality that is not cancer. False positives are inevitable in screening and very few tests will show cancer. If you want to have an ultrasound, ask and advocate for yourself.
WHAT IF MY DOCTOR WILL NOT ORDER ADDITIONAL SCREENING?
If you have dense breasts and would like an ultrasound, but your doctor will not order it, you can look into private facilities in your province that offer ultrasound without a doctor’s requisition.
Ontario Residents: There are two private clinics offering 3D Automated Breast Ultrasound (ABUS). ABUS was approved by Health Canada in 2011 as a screening tool. You do not need a doctor’s referral. More information about private options can be found in the Screening Options Section.
BC Residents: There are a number of facilities that provide ultrasound without a requisition. If you have or do not have a requisition, screening ultrasound is an out of pocket expense in BC (around $200)
WHAT IS 3D ULTRASOUND - AUTOMATED BREAST ULTRASOUND (ABUS)?
ABUS uses sound waves. Thousands of images are created and software reconstructs images in 3D.
Automated Breast Ultrasound (ABUS) was approved by Health Canada as a screening tool and as an adjunct to mammography for women with no symptoms for breast cancer. It is currently available privately in Ontario and under provincial insurance in Alberta.
3D Automated Breast Ultrasound (ABUS) can increase the rate of breast cancer detection by 35.7% in women with dense breast tissue.
Some private health plans pay a portion towards the use of ABUS.
More information about where you can access ABUS can be found in the Screening Options Section
SHOULD I CONTINUE TO GET MAMMOGRAMS IF I HAVE DENSE BREASTS?
Mammograms are proven to reduce breast cancer deaths. Mammograms can reliably detect suspicious calcifications.
Ultrasound/ABUS do not replace mammograms; they should be used in addition to mammography.
ADDITIONAL SCREENING OPTIONS FOR CANADIAN WOMEN WITH DENSE BREASTS
The following screening tests are described below: Mammography, Ultrasound, 3D Ultrasound (ABUS), MRI, Tomosynthesis.
Why is additional screening needed?
- Mammography reduces mortality from breast cancer, but it is an imperfect screening tool for women with dense breasts because it misses cancerous tumors about 50% of the time. 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.
What it is: Mammography x-rays the breast from different angles. A mammogram is the only way to find out breast density.
Positives: Over the past 30 years, mammography has helped reduce deaths through early detection by more than 35%.
Limitations: For women with dense breasts, dense tissue and cancer appear white on a mammogram, making it hard for cancer to be seen. Mammography uses low-dose radiation.
Accessibility: Screening mammography is available across Canada, except Nunavut. Digital mammography is widely available and is more accurate than analog mammography in dense breasts.
What it is: Ultrasound uses high frequency sound waves to image the breast.
Positives: When used with mammography, ultrasound increases the rate of cancer detection up to 97%. It detects an additional 3-4 cancers per 1000 women. It can detect cancer in dense breasts at an early stage. It is quick, safe, and non- invasive. No radiation is involved.
Limitations: Ultrasound is a very sensitive test and is generally used for diagnostic purposes, not screening. It may identify abnormalities that require additional investigation. Ultrasound alone is not recommended as a breast cancer screening tool.
Accessibility: A requisition for ultrasound is not usually given unless there has been a suspicious finding on a mammogram, MRI or a clinical breast exam. There may be a private clinic in your city where you do not need a doctor’s requisition and can pay directly.
AUTOMATED BREAST ULTRASOUND (ABUS)
What it is: This is a 3D ultrasound. Sound waves and software reconstruct breast images in a 3D plane.
Positives: ABUS can find small, invasive, node-negative cancers missed by mammography. ABUS was found to detect an additional 3.6 cancers per 1,000 women screened after mammography. When used with mammography, its effectiveness is from 94 to 97%. It is radiation free.
Limitations: ABUS may identify abnormalities that are not seen on a mammogram. Some of these abnormalities may require additional ultrasound or biopsy. Remember to resist the extra anxiety of false positives because most abnormalities are not cancerous.
Accessibility: Currently, ABUS can be found in Ontario and Alberta
In Ontario, patients must pay out of pocket for ABUS, but some private/group insurance plans may cover part of the cost. ABUS can be found in downtown Toronto and Barrie.
In Alberta, ABUS is covered under the provincial health insurance plan (AHIC) for women with dense breasts who qualify. A number of clinics offer ABUS.
MRI (MAGNETIC RESONANCE IMAGING)
What it is: It uses magnetic fields, radio frequency pulses, and a computer to produce detailed images of the breast..
Positives: MRI detects the most breast cancers of any imaging. It is an effective screening tool for women with dense breasts and detects 18 or more additional cancers per 1000 women. No radiation is involved. MRI is generally recommended for women with the highest cancer risk (those who carry the breast cancer gene, women who have had chest wall radiation for treatment of lymphoma, and some with rare genetic diseases)
Limitations: MRI is likely to generate more false positives requiring biopsy. It requires intravenous contrast injection.
Accessibility: MRI is available across Canada, but it is not used as a screening tool. It is currently used along with mammography for high-risk patients (BRCA gene, strong family history, or history of radiation to chest). There are a number of private pay MRI locations in Canada, but a physician’s referral is required.
What it is: Also known as 3D mammography, it creates multiple thin slices of images so that overlapping tissue is less likely to hide a cancerous tumour. The patient is positioned exactly the same way as for standard mammography.
Positives: Tomosynthesis increases the detection of invasive tumours over digital mammogram by an additional 1-2 cancers per 1000 women. When used with mammography, it decreases the false positive rate.
Limitations: Tomosynthesis does not detect as many cancers in dense breasts as ultrasound. The radiation dose may be higher than regular mammography because image acquisition takes longer. When used along with regular mammography, the radiation dose is slightly more than double.
Accessibility: Currently, Tomosynthesis is mostly being used for diagnostic purposes after an abnormality is found. However, In Alberta, patients visiting certain clinics are screened with both 2D mammography and tomosynthesis. Clinical studies are taking place in Canada to evaluate the role of tomosynthesis in screening for breast cancer.
The Dense Breasts Canada website is intended for the general purpose of:
1. Raising awareness about dense breasts and
2. Encouraging advocacy for the reporting of dense breast tissue to women.
We have included references, where applicable to ensure that the information provided is evidence based. However, we cannot guarantee that the information on the site is error-free or complete. The website is not intended to be a substitute for medical advice from a doctor. For answers to specific health-related questions, please consult your doctor. While we speak of Automated Breast Ultrasound (ABUS), we are not affiliated in any financial way with any private clinics that offer ABUS.