How Reliable Is Mammographic Assessment of Breast Density?

July 18, 2016

How Reliable Is Mammographic Assessment of Breast Density?

  1. Andrew M. Kaunitz, MD

Observational analysis of large data set finds wide variation in density assessment by radiologists.

  1. Andrew M. Kaunitz, MD

Having mammographically dense breasts impedes performance of screening mammography and has been associated with excess risk for breast cancer. Radiological categories of breast density are: almost entirely fat, scattered fibroglandular densities, heterogeneously dense, or extremely dense (the first two categories defined as “nondense” and the latter two as “dense”). Many states have mandated that information on breast density be communicated to women, focusing attention on supplemental breast imaging. Investigators analyzed prospectively collected observational data from screening mammograms performed between 2011 and 2013 (145,123 women, 216,783 screens; mean age, 58; 80% non-Hispanic white) from 30 U.S. radiology centers (83 radiologists). Data on consecutive screens were available for 45,313 women.

Overall, 37% of mammograms were assessed as dense. Radiologists varied substantially in assigning the four breast density categories. Based on the “dense versus nondense” classification, 25% of radiologists rated <29% of mammograms as dense, while 25% indicated ≥51% were dense. The least variation among ratings occurred for the “extremely dense” category. Among women with consecutive mammograms read by different radiologists, differing density categories between readings were noted in 33%. When stratified as dense versus nondense, consecutive readings were discordant 17% of the time for different radiologists and 10% of the time for the same radiologist.


The substantial variation among radiologists regarding breast density assessment supports previous guidance from the American College of Obstetricians and Gynecologists and others that a screening mammography report of dense breasts should not routinely trigger a recommendation for supplemental breast imaging (NEJM JW Womens Health May 2014 and Obstet Gynecol 2014; 123:910; NEJM JW Womens Health Jun 2015 and Ann Intern Med 2015 May 18; [e-pub]). However, when radiologists report extremely dense breast tissue, clinicians may consider recommending that the subsequent screen include concomitant breast tomosynthesis (NEJM JW Womens Health Jun 2016 and JAMA 2016 Apr 26; [e-pub]).

Editor Disclosures at Time of Publication

  • Disclosures for Andrew M. Kaunitz, MD at time of publication Consultant / Advisory board Allergan; Bayer AG; Merck; Pfizer Royalties UpToDate Grant / Research support Therapeutics MD; Bayer; Agile; Merck Editorial boards Contraception; Menopause; Contraceptive Technology Update; OBG Management; Medscape OB/GYN & Women’s Health Leadership positions in professional societies North American Menopause Society (Board of Trustees)


Reader Comments (2)

Kurt Elward, MD Physician, Family Medicine/General Practice

The data only support 3D too IF there is sufficient density. This study calls into question the validity of these density interpretations. Along with the strong push to do 3D (for additional reimbursement) despite the additional radiation in most current forms, this puts a tremendous number of women and their primary care physicians in a difficult position. We don't want to miss Cancer but with the uncertainty this study demonstrates, we can't be sure we are not overexposing women to unnecessary radiation and procedures.

Jayaraj Govindaraj Physician, Radiology, Apollo Specilaity-Cancer Hospital, Chennai, South India, PIN-600035

I must agree that this is a valid point to be kept in mind.
Additional Imaging can be done considering the level of patient anxiety, physicians suspicion levels and of course the calculated risk in the individual patient based on clinical interrogation at the time of initial mammography.
We always do a 3D Tomosynthesis analysis in all our patients with dense breasts and complement it with Ultrasound done by a reasonably experienced radiologist at our centre.
This might lead to a MR Mammogram & a Targeted Biopsy or WGL with precise excision if suspicions arise.

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