Fibrous, glandular and fatty tissues make up breasts. The first two tissues are connective and produce milk, if one has more of these fibrous and glandular tissues, it is also called “fibroglandular tissue” and the breasts are denser. For most women, breasts become less dense with age. Dense breasts are not a medical condition, it is rather normal. But the denser the breast, the higher the risk for breast cancer. A woman is 4 to 6 times more likely to get breast cancer than a woman that has more fatty tissues.

Worldwide, breast cancer is the leading cancer type in women. According to the US National Cancer Institute, common breast cancer symptoms are a lump in a breast, a change in breast shape, dimpling of the skin, fluid from the nipple, a newly inverted nipple or a red scaly patch of skin on the breast. To detect breast cancer in its early stages, the breast density plays an important role.

Cancer cells are formed in the tissues of the breast; therefore, breast cancer can be detected by a tissue biopsy or a mammography. The early detection of breast cancer is the goal of a mammography by using low-energy X-rays. A mammography is also the only tool that makes the density of the breast visible. The graphic below depicts how the visibility of the cancer depends on the density of the breast.


breast density

Source: courtesy of and Dr. Wendie Berg

It is important for women to do a mammography to know whether they have dense breasts. For doctors it is harder to detect breast cancers on a mammography of a woman with dense breasts. Consequently, there is a higher risk to miss cancers. In addition to the problems of detecting cancer in dense breasts, this condition also leads to a higher risk of getting breast cancer for which the reasons are still unclear. But dense breasts must be considered along with other risk factors. Besides being a woman, the biggest risk factors are the family history, obesity, some forms of hormone replacement therapy and others.

The key role of detecting breast density in the fight against cancer are regular mammograms. Patients must let the doctors and nurses know of their medical history and if there is anything that increases the risk for breast cancer, like the breast density. Based on a mammogram, radiologists read the results using the Breast Imaging Reporting and Data System (BI-RADS). This standard system uses an assessment scale from 1 through 6 to indicate, if or how cancerous the findings are. Additionally, the BI-RADS includes a score for breast density on a scale from A through D.

  1. A) Mostly fatty: The breasts are mostly made of fatty tissue, which accounts for about 10% of the women. Based on the density, the risk for breast cancer is rather low.
  2. B) Scattered “fibroglandular” densities: There are scattered areas of dense glandular and fibrous tissue, besides the breast being mostly fatty tissue. An estimated amount of 40% of women has scattered density.
  3. C) Heterogeneously dense: The mammogram reveals that more of the breast is made of dense glandular and fibrous tissue. Seeing small tumors in or around the tissues is very hard. 40% of women are associated with this category.
  4. D) Extremely dense: Breasts are extremely dense because they contain large amounts of “fibroglandular” tissues and about 10% of women fall into this category.

Women typically did not receive information about breast density in the past. This has been changing over the past decade. Besides the need for more awareness among women and better practices in hospitals and among radiologists to directly transfer the knowledge about the breast density based on mammography to the patient, there is a need for more intelligent solutions. Mammography results need to be constantly saved and updated in a patient’s health record. The goal is to advance the early detection of breast cancer by having a more intelligent and inclusive system.


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