3D vs 2D mammography for detecting cancer in dense breasts

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In which categories of breast density (FIGURE 1) does tomosynthesis/3D mammography increase cancer detection over standard digital mammography?

Fatty (category A) and scattered fibroglandular density (category B) only

Heterogeneously dense (category C) and extremely dense (category D) only

Fatty (category A), scattered fibroglandular density (category B), and heterogeneously dense (category C) only

All breast densities (categories A, B, C, and D)

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C. Overall, tomosynthesis depicts an additional 1 to 2 cancers per thousand women screened in the first round of screening when added to standard digital mammography;1-3 however, this improvement in cancer detection is only observed in women with fatty breasts (category A), scattered fibroglandular tissue (category B), and heterogeneously dense breasts (category C). Importantly, tomosynthesis does not significantly improve breast cancer detection in women with extremely dense breasts (category D).2,4

Digital breast tomosynthesis, also referred to as “3-dimensional mammography” (3D mammography) or tomosynthesis, uses a dedicated electronic detector system to obtain multiple projection images that are reconstructed by the computer to create thin slices or slabs of multiple slices of the breast. These slices can be individually “scrolled through” by the radiologist to reduce tissue overlap that may obscure breast cancers on a standard mammogram. While tomosynthesis improves breast cancer detection in women with fatty, scattered fibroglandular density, and heterogeneously dense breasts, there is very little soft tissue contrast in extremely dense breasts due to insufficient fat, and some cancers will remain hidden by dense tissue even on sliced images through the breast.

FIGURE 2 shows an example of cancer that was missed on tomosynthesis in a 51-year-old woman with extremely dense breasts and right breast pain. The cancer was masked by extremely dense tissue on standard digital mammography and tomosynthesis; no abnormalities were detected. Ultrasonography showed a 1.6-cm, irregular, hypoechoic mass at the site of pain, and biopsy revealed a grade 3 triple-receptor negative invasive ductal carcinoma.

In women with dense breasts, especially extremely dense breasts, supplemental screening beyond tomosynthesis should be considered. Although tomosynthesis doesn’t improve cancer detection in extremely dense breasts, it does reduce callbacks for additional testing in all breast densities compared with standard digital mammography. Callbacks are reduced from approximately 100‒120 per 1,000 women screened with standard digital mammography alone1,5 to an average of 80 per 1,000 women when tomosynthesis and standard mammography are interpreted together.1-3


For more information, visit medically sourced Comprehensive resources include a free CME opportunity, Dense Breasts and Supplemental Screening.

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