Screening for Women with Dense Breasts

By Priyanka Varma, Barbara Guido

BURLINGAME, Calif. Nov 17th, 2021

50% of women undergoing screening mammograms are classified to have “Dense Breasts”, which loosely translates to 4.5 million women [1, 2]. What is a “Dense Breast”? Breast is composed of fibrous, glandular and fatty tissue. Its distribution can range from entirely fatty to scattered areas of fibroglandular density to heterogeneous density to having almost entirely glandular and fibrous tissue. Women falling under the last two categories of “heterogeneous density” and “almost entirely glandular and fibrous tissue” are classified as having “Dense Breasts” [1; Fig 1].

Fig 1: Classification of Breast Density A: Almost Fatty B: Scattered areas of fibro glandular density C: Heterogeneous (many area of glandular and connective tissue) D: Extremely dense (almost entirely glandular and fibrous tissue)

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The accuracy of a mammogram is dependent on breast density. Up to 20% of breast cancers are not seen on mammograms leading to a false-negative result. A false negative result means that a mammogram appears to be normal even though a cancer is present. One of the causes of false negative results is dense breasts. Younger women (40-49 years) tend to have dense breast tissue and hence false negatives occur more often in younger versus older women [3, 4]. Pregnant women, breastfeeding, hormone replacement therapy (HRT), and lower body weight are other factors contributing to dense breasts [5].

On the other hand, a false positive mammogram looks abnormal even in the absence of cancer. This often leads to the patient undergoing several supplemental tests including invasive biopsies. It is more likely to get a false positive test result in the “screening” mammogram as compared to women who have been undergoing yearly mammograms. About 12% of women undergoing screening mammograms will need additional imaging or biopsy but most of them (95%) end up with a negative result [6]. False positive mammograms are also more prevalent in younger women, women with dense breasts, and women undergoing Hormone Replacement Therapy [3].

Despite the above limitations, per the current recommendations, the best methods available for screening breast cancer are high quality screening mammograms and clinical breast exams [3].

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