Understanding the Risks of Dense Breasts

Following a mammogram, many women are told that they have dense breasts. This is a common and normal finding. 

But what should you do with this information? Do women with dense breasts have a higher risk for breast cancer?

What is breast tissue made of?

• glandular tissue (milk glands), milk ducts, supportive/connective/fibrous tissue (dense breast tissue)
• fatty tissue (non-dense breast tissue)

When viewed on a mammogram, fatty breast tissue looks dark and transparent, and fibrous and glandular tissues appear white. This contrast makes it possible for radiologists to see and identify abnormalities within the breast.

Who is more likely to have dense breast tissue?

Younger women 

Breast tissue typically gets fattier with age.

Women with a lower BMI 

Women with less body fat are likely to have less fatty, more dense breast tissue (compared to women who are obese).

Post-menopausal women on hormone replacement therapy

Combination hormone therapy (used to relieve menopause symptoms) can increase breast density.

If you’re told you have dense breasts:

This means that your mammogram shows more fibrous and glandular tissue (predominantly “white” tissue, harder to see through) than fatty tissue. Because breast tumors may have the same density or “color” as the fibroglandular tissue, it’s difficult for radiologists to spot anything abnormal that might develop in the breast.

Breast density falls into four categories. 

1. Almost entirely fatty breast tissue (about 10% of women)
2. Scattered areas of fibroglandular density (about 40% of women)
3. Heterogeneously dense breast tissue (about 40% of women)
4. Extremely dense breast tissue (about 10% of women)

If you have dense breasts, ask which category applies to you.

Do denser breasts raise cancer risk?

The short answer is yes. 

Women with higher-density breasts have about four times higher risk of developing breast cancer than those with lower-density breasts. Oncology researchers are working to understand why this happens. The good news? 

Women with high-density breasts are NOT more likely to die from breast cancer.

Additional screenings for dense breasts

Regardless of breast density, annual mammograms are recommended for all women with an average risk of developing breast cancer, starting at age 40 through age 74 (at least). 

As women grow older, their breasts become fattier and less dense. Women who continue to have dense breast tissue, especially after menopause, have a higher risk of developing breast cancer. 

Higher-risk women should start their annual screening mammograms earlier than 40 years old. These include women who: 

• have a strong family history of breast and/or ovarian cancer
• carry genetic mutations that increase the risk of developing breast cancer
• received radiation therapy at a young age to treat lymphoma

If a mammogram reveals you have dense breast tissue, ask your doctor if one or more imaging modalities could provide a clearer picture of what’s happening inside your breasts.

3-D mammogram (digital breast tomosynthesis)

• Uses X-rays to take multiple images from different angles to create a 3-D image of the breast
• Increased breast cancer detection rates (about one to two additional cancers per 1,000 women)
• Reduces the need for additional testing

Breast MRI

• Uses an IV contrast dye and a magnet (not radiation)
• Recommended for women with a high risk of breast cancer
• Detects about 15 additional cancers per 1,000 women 
• Likely to find noncancerous areas that require additional testing

Breast ultrasound

• Uses sound waves (not radiation) to analyze tissue
• Commonly used to view areas of concern seen on a mammogram
• Detects an additional two to four cancers per 1,000 women
• Likely to find noncancerous areas that require additional testing

Molecular breast imaging (breast-specific gamma imaging or positron emission mammography)

• Uses a special gamma camera to record the activity of a radioactive tracer that’s injected into an arm vein
• Detects about seven additional cancers per 1,000 women
• Less likely to find noncancerous areas of concern     
• Exposes you to low radiation dose (but higher than mammography)
• Performed every two years in addition to an annual mammogram

Written by Dana Kantrowitz, a contributor for UHealth’s news service. Medically reviewed by Nicole Brofman, M.D.​, a breast radiologist with Sylvester Comprehensive Cancer Center, part of the University of Miami Health System.

If you are identified as high risk for breast cancer, Sylvester’s multi-disciplinary care team will work with you to create a plan with preventative and therapeutic interventions to decrease the risk of or to detect cancer as early as possible. Learn your risk level. Call 305-689-RISK (7475).

Tags: breast cancer care in Miami, breast self exam, clinical breast exams, diagnostic mammogram, high risk breast cancer, high risk cancer, magnetic resonance imaging mri, mri machine