Understanding How Breast Density Changes with Age

Breast density refers to the proportion of tissues that make up your breasts. All breasts have:

• Fibrous tissue — the matrix that holds the breast’s shape
• Glandular tissue — the lobes that make and the tubes that carry milk
• Fatty tissue — gives breasts their size and shape

Only about 10% of women have breasts that are composed mainly of fatty tissue. Fatty breasts are the easiest to interpret on a screening mammogram because fatty tissue appears gray, while cancerous tissue is white.

The denser your breasts are, the more difficult it is to distinguish breast tissue from cancer. Fibrous and glandular tissue show up as white on the mammogram, so it’s difficult to isolate a tumor from normal tissue. 

Joseph Calandra, MD, and Karen Mass, MD, our breast experts at Mass Medical Imaging, encourage you to understand your breast density and how it may change over your lifetime. We offer screening mammograms, diagnostic mammograms, and dense breast evaluations at our Lake Forest offices.

Young breasts are denser

Perhaps not surprisingly, young breasts tend to have more fibroglandular tissue than older breasts. Younger women don’t usually have mammograms, but researchers have documented the density of their breasts using other modalities. Density usually increases during pregnancy and breastfeeding as well.

You’re also more likely to have dense breasts if you’re lean. The less fat you have distributed throughout your body, the less fatty your breasts are, too. In fact, up to 60% of women at a healthy weight have dense breasts, compared with 20% of those who are overweight or obese. 

Density may decrease after menopause

When your hormones shift downward during perimenopause and menopause, your breasts may become less dense. Hormonal shifts may lead to weight gain, causing your breasts to contain more fatty tissue.

Between 50-60% of women aged 40-44 have dense breasts. In contrast, only 20-30% of women aged 70-74 still have dense breasts. 

However, if you take hormonal replacement therapy (HRT), your breasts may retain their density or lose it more gradually. Although breast density goes down with age, breast cancer risk goes up.

Dense breasts need extra screening

Breast density makes it more difficult to detect tumors on mammograms. Since early detection and treatment are key factors in curing breast cancer, visibility of small tumors is important. 

In addition, women with dense breasts have a higher risk of breast cancer in general. That’s because tumors tend to form in fibroglandular tissue, not fatty tissue. If you have more fibrous and glandular tissue, you then have more places where cancer could form. 

However, just because you have dense breasts, that doesn’t mean you’ll get breast cancer. Women with an average risk of breast cancer have a one in eight chance of developing the disease during their lifetime. Those with dense breasts have a 1 in 6 or 7 chance of developing breast cancer. That’s a jump of up to 15%, but the risk is still low.

You can minimize that extra risk with careful screenings. In addition to a regular screening mammogram, you may need an automated breast ultrasound (ABUS) for dense breasts. The ultrasound can visualize areas that aren't clear on mammograms. However, ABUS is an adjunct to, not a replacement for, mammograms.

To schedule your mammogram, ABUS, or dense breast evaluation, call our friendly staff at 847-235-2415 or book online via our appointment form.