Women with Dense Breasts and Additional Screenings

A study supported by the National Cancer Institute (NCI) found that people with dense breasts can benefit from a screening strategy that is not limited to following up a negative mammogram with additional screenings such as an ultrasound, a PET scan, or an MRI. The study suggests that the best predictor of a person developing a breast cancer after having a negative mammogram, and before her next mammogram, is a screening strategy that also takes into account other risk factors such as age, race, family history, and history of breast cancer biopsies.

Breasts have a mixture of fibrous and glandular tissue and fatty tissue. Breasts are considered dense if you don’t have much fat but instead have a lot of fibrous or glandular tissue. The only way you would know your breast density is if you had a mammogram. Only a radiologist can determine your breast density—you can’t feel it. Firm breasts don’t mean dense breasts. 

four categories of breast density
Verywell / Jessica Olah

There are four categories used to describe breast density:

  1. Breasts that are the least dense have almost all fatty tissue
  2. Breasts that have scattered areas of fibroglandular density
  3. Breasts with heterogeneous density
  4. Breasts that have almost all glandular and fibrous tissue with little to no fatty tissue.

Dense breasts can make finding a cancer more difficult on a mammogram. Yet, mammograms are still considered to be the screening tool of choice for those who have dense breasts. Whenever possible, a person with dense breasts should have a digital mammogram as digital has proven to be a more effective screening tool than the traditional film mammogram.

Dense breasts show up on mammograms as white, and, as such can hide a tumor, since cancer also shows up as white. So additional tests are given to rule out any cancer not picked up in a mammogram.

Dense breasts are not uncommon. About half of people getting mammograms have dense breasts. Dense breasts are more common in younger people, and people who take hormone therapy to relieve signs and symptoms of menopause.

Having dense breasts is considered an increased risk for breast cancer. High breast density often causes false-negative findings on a screening mammogram.

Concern over the increased risk for breast cancer in people with dense breasts has resulted in national legislation that mandates doctors to inform people if they have dense breasts, and to discuss having additional imaging such as MRI, PET, or ultrasound following a normal mammogram.

The Risk of False Positives

While additional imaging can find breast cancers that are missed in a mammography, these imaging procedures may result in increased numbers false-positive results. False positives necessitate having more procedures, which include the pain and anxiety of unnecessary biopsies.

The study, led by Karla Kerlikowske, M.D., of the University of California, San Francisco, was published in the Annals of Internal Medicine.

Data used in the study came from more than 365,000 women ages 40 to 74 years in the Breast Cancer Surveillance Consortium (BCSC), an NCI funded program. A five-year breast cancer risk for each person took into consideration breast density, age, race, any family history of breast cancer, and history of breast biopsies to estimate breast cancer risk over the next five years.

Researchers found that about 47% of the subjects had dense breasts, and those at highest risk of getting a cancer between mammograms were those having 75% of their breast tissue considered dense tissue.

The BCSC risk calculator is designed as a tool to assist clinical decision-making. Primary care providers can calculate a 5-year breast cancer risk using the risk calculator and use this information in their discussions about supplemental or alternative screening methods in people with dense breasts. The risk calculator can also be used to compare one person's risk relative to the average risk for a person of the same age and ethnicity.

"This study is a good example of using information wisely to personalize risk estimation,” said Stephen Taplin, M.D., M.P.H., of NCI’s Division of Cancer Control and Population Sciences.

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  1. Kerlikowske K, Zhu W, Tosteson AN, et al. Identifying women with dense breasts at high risk for interval cancer: a cohort study. Ann Intern Med. 2015;162(10):673-81. doi:10.7326/M14-1465.

  2. NCI Staff. Many Women with Dense Breasts May Not Need Additional Screening. National Cancer Institute.