Harvard Health Letter

Caution: Cancer risk elevated in women with dense breasts

But new research offers reassurance that dense breasts don't raise risk of cancer death.

Dense breast tissue can make it harder to see breast cancer on a mammogram. Dense breasts have more glandular and fibrous tissue and less fatty tissue. Past research has found that women with dense breasts are more likely to get breast cancer. Higher blood levels of estrogen raise the risk both of dense breasts and breast cancer, possibly explaining the link. The association is so important that five states have now passed laws requiring that women whose mammograms show dense breasts must be notified of this fact.

Comparing two mammograms

Comparing two mammograms



Breast scans courtesy of Radiological Society of North America

The breast on the left is mostly fat,
which appears gray; the breast on the right
is mostly dense tissue, which appears white.
Tumors and other abnormalities also appear white,
so they can be difficult to spot in dense tissue.

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