How Do I Know if I Have Dense Breast Tissue?

Every woman who participates in breast cancer screening must know the answer to this critical question


I only learned that I had dense breasts after my startling, completely unexpected diagnosis of advanced stage breast cancer in 2004. For the previous 11 years I had participated in annual mammography screening, knowing that breast cancer detected early is the easiest to treat. But I was never told that having dense breast tissue made the mammogram x-rays less sensitive to detecting cancer. Little did I know that year after year, my “normal” mammogram results had been inaccurate.

When my cancer was finally diagnosed because it grew large enough to be felt, it was in an advanced stage: it had spread to 13 lymph nodes and was 3 times larger than an early-detected cancer would have been. Unfortunately, the size of the cancer and the degree of lymph node metastasis greatly affect the likelihood of breast cancer survival.

Nancy Cappello.
Nancy awaiting 9-hour surgery a few months after her eleventh normal mammogram
Joseph Cappello

What are Dense Breasts?

Breasts are comprised of fatty and glandular tissue; dense breasts have less fat and more glandular tissue. Dense breast tissue has a “masking effect” on potentially cancerous masses, because they both appear white in mammogram images, and there is little visual contrast to help detect tumors. Research shows that the denser the breast tissue, the less reliable the mammogram results are.

Having dense breast tissue is common; 40 percent of all women have it. As you age, breast tissue tends to become more fatty than glandular in composition — but not for everyone. (Even in my seniority, my one remaining breast is still dense!)

Two-thirds of premenopausal women and one quarter of postmenopausal women have dense breast tissue. The American College of Radiology reports that women with dense breast tissue are at a higher-than-average risk of breast cancer.

Identifying Dense Breasts

Categories of dense breast tissue.
Categories of Dense Breast Tissue
Are You Dense Inc.

There are four categories of breast tissue – (A) fatty, (B) scattered, (C) heterogeneously dense, and (D) extremely dense. A radiologist determines the density of a woman's breasts by examining a mammogram. While not mandated under the federal Mammography Quality Standards Act, radiologists have been reporting a woman's dense breast tissue to her referring doctor for decades.

I was stunned when I found, buried in my health records, 11 reports from the radiologist to my primary care physician, stating that I had extremely dense breast tissue which could lower the sensitivity of my mammograms. The mammogram result reports that I had received for the past 11 years said nothing about dense breasts and the higher likelihood that cancer could go undetected.

I am outraged that this information was withheld from me and many other women who have dense breasts. If early detection matters, there is a large subset of the population, those of us with the dense breasts, that do not have equal access to an early diagnosis. This inequity in breast screening could be lethal.

Inspiring the Density Reporting Movement

Landmark legislation passed in Connecticut in 2009, which was inspired by my experience, has fueled the density reporting movement across the United States and the world. As of this publication, 36 states have enacted density reporting legislation. Women in the United States who reside in these states must receive information about dense breast tissue in their mammogram results report.

State breast density reporting.
U.S. Map of “Dense” Legislation
Are You Dense Inc.

Based on my experience, here are my breast health recommendations.

  1. Do not rely on your normal mammography reporting results as the definitive answer to whether you have breast cancer.
  2. Request copies of the radiologist’s report from your primary care doctor and compare its findings to your mammography reporting results.
  3. Discuss your breast tissue density and breast cancer risk with your primary care physician and/or breast radiologist, as well as personalized screening beyond the 2D or 3D mammogram.
  4. Ask your health care provider how confident s/he is that there is not a cancer hidden within your dense breast tissue that did not show up on your mammogram.

The Are You Dense brochure and the Handy Guide to Screening Patients with Dense Breasts can help you pursue these conversations, and collaborate with your provider to create a personalized screening plan. Remember – you are ultimately your own best health advocate.

See more helpful articles:

'Are You Dense?' Be Smart About Your Raised Breast Cancer Risk With Dense Breast Tissue

FDA Approves Genius 3D Mammography: Best Exam for Women with Dense Breasts

Turning Forty? Do You Need a Mammogram?