What is it?

A mammogram is a low-dose X-ray of the breast used to identify abnormalities, including early signs of breast cancer. It remains the gold standard for breast cancer screening in average-risk populations.

 

How Does it Work?

Mammograms capture detailed images of breast tissue, helping radiologists detect abnormalities based on differences in tissue density:

• Tumors and dense glandular tissue absorb more X-rays, appearing white on the image.

• Fatty tissue absorbs fewer X-rays, appearing darker, making abnormalities easier to spot in less dense breasts.

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2D Mammogram:
Takes two flat X-ray images of each breast—one from the top and one from the side.

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3D Mammogram (Tomosynthesis):
Gathers multiple images from different angles to create a layered, three-dimensional view of the breast.

• Detects 1 to 2 more cancers per 1,000 women screened compared to 2D mammograms.

• Lowers the number of callbacks (recalls) to about 84 per 1,000 women screened.

• Evidence about its effectiveness specifically for women with dense breasts is mixed, with minimal benefit suggested.

• Important: 3D mammography is still considered a standard screening tool, not a supplemental screening method.

• Around 87% of mammograms done in the U.S. use 3D technology.

 

Best for:

Detecting early signs, including microcalcifications of breast cancer in average-risk women. 

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​Clinical Performance:​

• Sensitivity may be as high as 99% in women with fatty breast tissue.

• Sensitivity may be as low as 30% in women with extremely dense breast tissue. (2)

• For women with a ≥20-25% lifetime risk: sensitivity ranges from 25% to 58%, with specificity between 93% and 100%. (3)

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Limitations:

• Reduced effectiveness in women with dense breast tissue, increasing the likelihood of false negatives.

• May miss up to 30% of interval cancers (4)

• Field of view limitations

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​Regulatory Status:

Approved for screening and diagnostic use. Providers are required to ensure compliance with dense breast notification laws, which mandate informing patients about their breast density and its potential implications for cancer risk and screening effectiveness.

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Important to Know:​​

• Discuss breast density with patients during screening discussions, emphasizing its impact on mammogram sensitivity and breast cancer risk.

• For women with dense breasts, engage in shared decision-making to explore additional screening options that align with their individual risk factors, available resources, and personal values.

• Stay informed about state legislation regarding dense breast notifications and insurance coverage for supplemental imaging.