By Annette Pinder

According to the U.S. Centers for Disease Control and Prevention (CDC), breast density refers to the amount of fibrous and glandular tissue in a woman’s breasts, compared with the amount of fatty tissue that can be viewed on a mammogram. A mammogram determines a woman’s breast density, which is characterized into four categories.

  1. Breasts are almost entirely fatty (about 10% of all women).
  2. Few areas of dense tissue are scattered throughout the breasts (about 40% of all women).
  3. Density is distributed evenly throughout both breasts (about 40% of all women).
  4. Breasts are extremely dense (about 10% of all women).

Women identified in the first two categories have low-density, non-dense, or fatty breasts, and women classified in the second two categories have high-density or dense breasts. About half of women 40 years or older have dense breasts.

“Breast density is important, as women with dense breasts are at a greater risk of being diagnosed with breast cancer,” explains Dr. Asha Ziembiec. Also, the denser the breasts, the higher the risk. Dr. Ziembiec also says it is important to know that individuals diagnosed with breast cancer who do have dense breasts are at a slightly greater risk of developing the disease than are patients with non-dense breasts.

“Still, it is important to know that dense tissue can hide cancers. For example, fibrous and glandular tissue appears white on a mammogram, the same as a possible tumor. This can make it difficult to identify whether a person has a tumor or dense breast tissue on a mammogram. It is also the reason why a small tumor can be missed,” says Dr. Ziembiec. There are, however, different studies that show that some tumors that might be missed on a mammogram can be visualized with other types of screenings. These include breast ultrasound, which uses soundwaves to obtain images of areas inside the breast, and breast magnetic resonance imaging (MRI), which uses a magnet linked to a computer to view detailed pictures of areas inside the breast.

The CDC notes that women who are more likely to have dense breasts are those who are younger; pregnant or breastfeeding; taking hormone replacement therapy; and have a lower body weight. While researchers don’t know why there is a relationship between dense breasts and a greater likelihood of being diagnosed with breast cancer, or why some women with dense breasts develop cancer while others do not, they are continuing their research to learn more. In fact, they are also researching if women can reduce their breast density.

The physicians at Southtowns Radiology recommend that all women receive a baseline mammogram at age 35, followed by annual breast cancer screening starting at age 40. Learn more at where you can submit a request for an appointment online for either the Hamburg or Orchard Park office, or call 716-649-9000 and select option 1.

Wondering about your own risk? Use the breast cancer risk assessment tool provided by the National Cancer Institute at