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Breast Density

Breast Density and Notification

The density of the breast on a mammogram is an important indicator of risk, equivalent to a first-line family history of breast cancer. Breasts are composed of fat, glandular tissue and supporting fibrous structures. The more fibro-glandular tissue is present, the greater the breast density will be on the mammogram.

Women with the highest breast density have approximately five times the risk of developing breast cancer compared to women with the least dense breasts. Every 1% increase in breast density is equivalent to a 2% increased risk of breast cancer. In addition to this increased risk, high density lowers the accuracy of mammography. Women with above average density account for half of all those presenting with breast cancer within one year of a ‘negative’ screening mammogram.

The importance of Breast Density has been recognised in the United States, where there is a Federal Density Bill. At present, nineteen States including New York and California have enacted legislation which requires that a woman is informed of her breast density following mammography. She will also be informed of the implications of high density and the possible need for supplementary examination such as breast ultrasound. Though mammography remains the more accurate test, additional ultrasound significantly increases the number of small cancers detectable in women with dense breast tissue.

Image showing State Mandatory Breast Density Notification in USA, taken from

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