Dense breasts



Breast density is a measure used to describe mammogram images.

Mammographic breast density (MBD) is a radiologic estimate of  the amount of radiopaque or highly dense breast tissue composed of epithelial and stromatolites elements compared with the amount of radiolucent or low density fatty tissue.

Fatty tissue appears dark or radiolucent because it absorbs fewer x-rays, whereas epithelial and stromatolites elements appear white or radiopaque because they filter the x-rays efficiently and absorb more energy.

Breasts are made up of fat and breast tissue, the milk ducts and lobules, called glandular tissue.

Breast density compares the area of connective tissue seen on a mammogram to the area of fat.

Breast and connective tissue appear denser than fat on a mammogram.

Mammographic density is the result of differential penetration of breast tissue by x-rays and is the sum of other variables.

X-rays readily penetrate fat tissue, and a high relative volume of how to post tissue correlates with low mammographic density.

Epithelial and stromal tissue are relatively radiographically opaque and a high ratio of epithelial/stromal to adipose tissue is associated with a high mammographic density.

It is required that all mammogram reports include commentary on breast density, and patients be notified of results.

A high breast density indicates a greater amount of breast and connective tissue compared to fat.

Low breast density indicates a greater amount of fat compared to breast and connective tissue.

Some breasts are mostly fat.

Some breasts are mostly breast and connective tissue, indicating a dense breast.

Mammograms of dense breasts are more difficult to read than mammograms of fatty breasts.

A masking effect refers to situations where dense breast tissue obscure small, underlying breast lesions that have a mammographic attenuation similar to fibroglandular tissue being isodense.

With this lack of contrast small noncalcified breast cancers can be overlooked and lead to larger tumors with lymph node involvement and decreased survival rates.

Mammographic density is variable throughout a woman’s lifetime and is associated with age, menopausal status, and BMI.

Low mammographic density is associated with increased age and BMI, while high mammographic densities associated with young age and low BMI.

Weight loss and exercise is associated with increased mammographic density.

Older women and obese women have a decreased breast density relative to younger women in normal weight women, but this is not usually accounted for on BI-RADS breast density evaluation.

Women with high breast density are 4-5 times more likely to get breast cancer than women with low breast density.

Breast cancer does not develop in many women with dense breast tissue, but it is an independent risk factor for breast cancer.

In the U.S., 40-50 percent of women ages 40-74 have dense breasts.

Nearly 40,000,000 women undergo routine mammogram studies in the US each year and about 43% of these exams reveal the presence of dense breasts.

Breast density varies greatly by age and weight.

Dense breasts are more common in both young and thin women.

About 50-60 % of women 40-44 have dense breasts, compared to 20-30 percent of women ages 70-74.

About 50-60% of healthy weight women have dense breasts, compared to 20-30 percent of obese women.

Postmenopausal women on hormone therapy may have increased breast density.

Asian and Pacific Islander women have the highest prevalence of dense breasts.

Breasts become less dense and more fatty with age.

In a randomized trial Dense TIssue andEarly BreastNeoplasm Screening (TENSE) trial supplemental MRI screening in women with extremely dense breast tissue and normal results on mammogram resulted in the diagnosis of significantly fewer interval cancers than mammography alone during a two-year screening period.

Mammography has an overall sensitivity of 70 to 90% and the sensitivity of 80 to 98% among women with category a breast density; the sensitivity can be as low as 30 to 48% for women with category d breast density.

Among women with dense breasts undergoing screening breast MRI there is significantly higher rate of invasive cancer detection than digital breast tomosynthesis (Comstock CE).

Studies show that high mammographic density is associated with two to sixfold increased breast cancer risk (Northern European)

High density breast tissue is associated with a greater likelihood that a breast cancer will be missed on screening mammograms, consequently not detected until locally advanced.

Latin and Black women have a lower average mammographic density than Asian and White women.


In women with extremely dense breasts, digital breast tomosynthesis (DBT) does not outperform digital mammography (DM) after the baseline exam, according to a review of nearly 1.6 million screenings.

There were no significant differences in recall or cancer detection rates among women with extremely dense breasts in any age group.

Density should not be used as a criterion to triage use of DBT for routine screening.

Tamoxifen, aromatase inhibitors and selective estrogen receptor blockers reduce mammographic breast density and reduce breast cancer risk.

Many states have laws requiring health care providers to notify women found to have dense breasts on a mammogram.

Although dense breasts are associated with increased risk of breast cancer, it’s not clear that lowering breast density will decrease risk: getting older and gaining weight after menopause are both related to a decrease in breast density, but an increase in breast cancer risk.

There are no special recommendations or screening guidelines for women with dense breasts.

Mammographic breast density is found to be associated with alcohol intake suggesting an increase in estrogen production and aromatase enzyme activity, facilitating conversion of androgens to estrogen thus causing increased estrogen levels.

Alcohol increases insulin growth factor and insulin like growth factors which can increase mammory epithelial cell proliferation and synergistically work with estrogen to increase mammographic breast density.

Alcohol is a known risk factor for breast cancer, particularly estrogen receptor positive cancers and alcohol increases mammographic breast density in premenopausal and post menopausal women.

Caffeine can alter estrogen metabolism, and decrease circulating estrogen levels, and can lead to lower mammographic breast density.

While physical activity decreases the risk of breast cancer, it does not influence the degree of mammographic breast density.

Digital mammography has screening benefits over film mammography for women with dense breasts.

Requiring the notification of breast density may increase the use of other imaging tests in addition to mammography, and there is no evidence to suggest supplemental imaging for women with dense breasts improves cancer outcomes, including mortality.

Such additional testing may increase the false positive rate, increase unnecessary biopsies and presumably overdiagnosis.

Notification laws have had unintended consequences: inflating breast cancer risk in women of north European and Asian ancestry and minimizing risk in Latin and Black women: Black women have the highest burden of early onset breast cancer and breast cancer death therefore such notification lies minimize the risk in the very women who are in need of additional screening.

Women presenting for their first screening examination are particularly important to prioritize for DBT, regardless of breast density or age.


The investigators compared the performance of 1,273,492 DMs with 310,587 DBTs across the four Breast Imaging Reporting and Database System density types: almost entirely fatty, scattered fibroglandular density, heterogeneously dense, and extremely dense.

Approximately 50% of mammogram reports in the US are reporting as heterogeneously dense or extremely dense, and dense breast tissue is the most prevalent risk for breast cancer.

Breasts classified as Bi-RADS category a or b would be a generally referred to as low density breasts, whereas breasts in category c or d are referred to as high density breasts.

In women aged 50-59 years, screening recalls per 1,000 exams dropped from 241 with DM to 204 with DBT with a relative risk of 0.84.


Cancer detection rates per 1,000 exams in this age group increased from 5.9 with DM to 8.8 with DBT with a relative risk of 1.50.


Recall rates were lower with DBT for women with scattered fibroglandular density and heterogeneously dense breasts in all age groups, as well as in women with almost entirely fatty breasts aged 50-79 years.


There were no significant differences in recall rates in women with extremely dense breasts in any age group


Cancer detection rates are  higher with DBT than with DM in women with heterogeneously dense breasts in all age groups and in women with scattered fibroglandular density at 50-59 years of age and 60-79 years of age. 


Cancer detection rates are  not significantly different with DBT or DM for women with almost entirely fatty breasts or extremely dense breasts of any age.;


Population-based mammographic density studies demonstrate a clear association between high mammographic density and cancer risk, but this has not translated to risk prediction in individuals.


There is evidence that low mammographic density, rather than high density is associated with poor breast cancer survival and death.

There is an inverse association between consumption of a Mediterranean diet and MBD.

Diet with plant based foods and physical activity interventions demonstrate a modest decreasing the percentage of breast density compared to controls.

High carbohydrate intake in high glycemic loads are found to be associated with increased mammographic breast density.

High glucose levels lead to hyperinsulinism and subsequent activation of insulin receptors and elevated insulin like growth factor 1, with which works with estrogen and causes proliferation of mammary epithelium and hence increases MBD.

Smoking is inversely associated with mammographic  breast density.

BMI and mammographic rest density are inversely related to each other and are independent risk factors for breast cancer.

Menopausal hormonal therapy is associated with increased mammographic breast density, which may be associated with an increased risk for hormone positive breast cancer.

Hyperinsulinemia through exaggerates insulin administration has been implicated as a possible risk factor for breast cancer, and increased insulin levels are associated with increased mammographic breast density.

Patients with mammographic breast density should avoid smoking and limit alcohol intake, maintain an exercise program, adopting a Mediterranean diet, try to limit menopausal hormonal therapy.

In a study of 947 women attending a breast screening clinic for up to 10 years all women, regardless of subsequent breast cancer development, had a decrease in breast density: the rate of density change was significantly lower in the breast in which cancer was later diagnosed suggesting longitudinal evaluation in breast density from digital mammograms may offer additional tool for assessing risk of breast cancer(Jiang S).








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