Why is breast density important?
Breast density is an independent risk factor for breast cancer
High breast density increases a woman's chance of developing breast cancer in the future. The increased amount of glandular area and epithelium (the thin cell layer that lines the ducts and lobes) in dense breasts means there are more sites for cancer to arise. Additionally, the internal environment of dense breasts promotes cancer development. Women in the highest category of breast density have 4- to 6-fold higher risk of developing breast cancer than those in the lowest category.
Breast density masks cancer on a mammogram
Both cancers and dense tissue appear white on a mammogram. This means that a cancer is more likely to be missed in women with dense breasts. A cancer in a fatty breast will almost always be found, whereas an extremely dense breast can conceal a cancer almost half of the time. Furthermore, women in the densest breast category are almost 18 times as likely to develop interval cancers (cancers that are either missed or absent at the time of screening mammography) relative to women with fatty breasts.
Having high breast density is perfectly normal and does not necessitate that a woman will get cancer or any form of breast disease. However, women with dense breasts should discuss the impact that increased breast density has on masking risk and the risk of developing breast cancers with your physician.
In this video, Jean Weigert, MD, FACR, director of Breast Imaging at The Hospital of Central Connecticut, explains breast density and how it affects radiologists’ ability to detect cancers in mammography.