Breast Density and Mammography Quality

Studies have shown that women with extremely dense breasts are 4-6 times more likely to develop breast cancer, and poor quality screening mammograms are at a 2.5 times higher risk of ending up as interval detected cancers. 

Risk Factors

Population level breast screening focuses on early detection of breast cancer based on screening protocols which factor in a woman's risk profile.  When comparing all breast cancer risk factors, only age and genetic factors show as similarly strong associations with cancer risk as breast density. 

Obscuring Cancers

Dense tissue and poor quality images can obscure tumors, micro-calcifications and other information that is vital in detecting and diagnosing cancer.  Sensitivity measures the accuracy of a test in correctly identifying a condition. Generally, the sensitivity of mammography is 80 percent, but when breasts are dense, sensitivity can be as low as 50 percent.  

Precise Health

Patient-specific metrics on breast density and image quality help to inform precise health.  Breast density and image quality impact how women are triaged for follow-up screening modalities and frequency of follow-up screening visits.  Because of masking and decreased sensitivity, women with dense breasts (and other clinical risk factors) may be flagged for additional screening mammography or adjunctive imaging using whole breast ultrasound, MRI, or tomosynthesis.

Dense Breasts

Because of masking and decreased sensitivity, women with dense breasts (and other clinical risk factors) may be flagged for additional screening mammography or adjunctive imaging using whole breast ultrasound, MRI, or tomosynthesis.






                   Breast Density                                                and                               Breast Screening

Millions of women participate in breast cancer screening programs every year

Some programs are delivered at a state or provincial level, others on a per clinic basis.  These programs typically use full-field digital mammography as the first step to check for signs of breast cancer, evaluate individual risk, and make decisions about any additional screening modalities that might be beneficial.  The effectiveness of breast screening is heavily impacted by breast density.

Variable Reporting Standards

Reporting standards can vary significantly from radiologist to radiologist, clinic to clinic, and between jurisdictions.  As a result, significant effort has been made to improve the reporting guidelines, standards and legislation surrounding breast imaging and breast density. 

Intra-Radiologist Subjectivity

There can be substantial disagreement between radiologists assessing density on the same mammogram, or even by the same radiologist assessing density on the same mammogram at different times. 

Reliability and Reproducibility  

The current practice of visual assessment of breast density is not standardized, precise or reproducible.  Accuracy, reproducibility, and reliability of breast density measurements are critical factors in ensuring equitable and consistent service delivery and application of clinical practice guidelines.

Mammography Guidelines, Standards, and Accreditation

National quality standards in mammography have been established to ensure safe, reliable, and accurate breast imaging services are delivered at accredited and certified facilities.  As these standards evolve, certified facilities are required to adapt and remain in compliance at all times.


In the United States, the Mammography Quality Standards Act (MQSA) is in place to ensure the consistent delivery of quality mammography services.  These quality standards require facilities to secure initial accreditation from an FDA-recognized body; receive certification as meeting the standards set out; participate in annual inspections to confirm compliance with the standards, and prominently display their certificate.  Additionally, EQUIP (Enhancing Quality Using the Inspection Program) was created to address Quality Assurance, clinical image quality, and Quality Control.

EQUIP is meant to demonstrate that every imaging centre has corrective measures in place that address when images are poor quality; ensures that images continue to comply with accreditation standards; and has a process for QA/QC oversight.


In the European Union, the European Reference Organization for Quality Assured Breast Screening and Diagnostic Services (EUREF) works in collaboration with other organizations to set standards. 

Several activities are underway in the EU to support quality mammography services.  EUREF works in partnership with other organizations to set out mammography guidelines, certify breast services and mammography equipment, and provide training and counsel.  The European Society of Radiology (ESR) established the EuroSafe program as a driver to improve quality and safety in medical imaging.  This program covers a wide variety of areas, including radiation exposure; equipment maintenance; appropriate use; and communications with patients. 


In Canada, the Canadian Association of Radiologists sets out mammography standards.  The Canadian Association of Radiologist's Mammography Accreditation Program (MAP) is designed to ensure consistent delivery of quality mammography services through an accreditation process and established quality standards that are similar to those laid out in the MQSA. 

While these quality standards already exist, recent legislative changes are now beginning to impact the imaging and reporting processes.  Mammography facilities must now ensure compliance with both the quality standards and legislated reporting practices.

Breast Density Notification

Historically, when breast density has been recorded it has not been reported to a woman or her primary care physician.  This gap in patient knowledge is rapidly narrowing due to self-advocacy, which has led, in some jurisdictions, to the enactment of inform legislation.  Due to increasing awareness of the link between breast density, adjunct screening, and missed cancers, there is a public demand for change.

There is growing public demand to inform women of breast density. Individuals and advocacy groups are calling on state and federal legislators to introduce inform legislation that mandates breast density disclosure to women at the time of their mammography exam.  75% of women in the United States are covered by state legislation that requires them to be informed of their breast density.  There are active bills in a number of remaining states that have yet to pass inform legislation. As well, the Breast Density and Mammography Reporting Act bill is currently before the US Senate for review. 

In the UK, an All-Party Parliamentary Group on Breast Cancer maintains a focus within government on issues related to breast cancer and its prevention.  Breast Cancer Now, which provides the Secretariat to the APPG, is seeking to improve methods for assessing breast cancer risk by evaluating how genetic and non-genetic factors, including density, contribute to risk. 

As of 2016, doctors in some municipalities in Japan have started to inform women about their breast density category and the corresponding implications for screening. 

BreastScreen Australia is supportive of research that seeks to understand the role of density in frequency and modality of breast screening, as well as greater discussion and public awareness about breast density.