Breast Density: Know Your Body and Your Breast Cancer Risk

Sep 13, 2023 | Cancer

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Knowing whether you have dense breasts can help you better understand your risk of breast cancer.

New rules from the Food and Drug Administration empower women to make informed decisions about breast health by requiring mammography facilities to notify patients about their breast density.

Defining Breast Density

Breasts contain fibrous tissue for support, glandular tissue for making and transporting milk, and fatty tissue to give them shape. Breast density refers to how much fibrous and glandular tissue you have compared with fatty tissue on a mammogram. Dense breasts — those with a lot of fibrous and glandular tissue — increase the difficulty of identifying potentially cancerous masses. That’s because both masses and non-fatty tissue look white on a mammogram.

Radiologists use four categories to classify breast density:

  • Entirely fatty breast tissue. Fatty tissue accounts for almost all breast tissue.
  • Scattered fibroglandular breast tissue. Fatty tissue makes up the majority of breast tissue, but some fibrous and glandular tissues are present.
  • Heterogeneously dense breast tissue. Fibrous and glandular tissues are much more common than fatty tissue.
  • Extremely dense breast tissue. Fibrous and glandular tissues make up nearly all breast tissue.

Nearly 50 percent of women age 40 or older have heterogeneously dense or extremely dense breasts, according to the Centers for Disease Control and Prevention.

How Does Breast Density Affect Breast Cancer Risk?

Women with dense breasts have a higher risk of developing breast cancer. Researchers haven’t determined why dense breasts are a risk factor. One theory is that dense breast tissue provides more opportunities for abnormal cell growth, according to the American Cancer Society. Fortunately, there’s no evidence that dense breasts increase the risk of dying from breast cancer.

New Rules for Reporting Breast Density 

You can’t determine whether you have dense breast tissue based on your breasts’ appearance or texture. A mammogram is the only way to find out — and new federal standards for mammography facilities are making it easier.

In March 2023, the FDA updated regulations under the Mammography Quality Standards Act of 1992. The new rules require mammography facilities to include breast density results in the mammogram report they send to patients. The centers have to notify patients whether their breasts are dense or not dense and how breast density affects their cancer risk using easy-to-understand language.

The new standards also require mammography facilities to advise patients to discuss their breast density assessment with their physician. Under the new rules, the mammogram reports that physicians receive classify their patients’ breast density according to the four breast density categories.

The new rules for mammography facilities will come into effect on September 10, 2024. 

Make Time for a Mammogram

If a mammogram reveals that you have dense breasts, you shouldn’t stop breast cancer screening just because lumps and other masses may be more difficult to see. Mammography — especially 3D mammography, which may be better than 2D mammography at finding cancer in dense breast tissue — remains a valuable tool to detect breast cancer in women with dense breasts. You should have a screening mammogram each year beginning no later than age 40.

Talk with your primary care physician or gynecologist about whether you need to have more frequent breast imaging, based on your risk. Your physician may recommend other types of imaging for breast cancer detection, such as a breast MRI or ultrasound, to complement mammography.

Early detection is key to fighting breast cancer. Learn more about our breast health and imaging services across our health system.

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