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New Breast Density Legislation

What does the new legislation regarding breast density really mean? New Iowa legislation regarding mammography reporting brings changes to what will be included on the report you receive from your mammogram.


The state of Iowa has passed a new bill into legislation regarding mammography reporting taking effect in 2018. You can read the full bill. This bill requires information about a patient's individual breast density to be included in the report they receive from their mammogram. Details of an individual's breast density will be specified in the mammogram report based on predetermined national standards.

In preparation for this state-mandated change to reporting, here are some things to consider:

What is breast density?

The breast is made up of many different types of tissues. Breast density is a measurement used to characterize the relative amounts of each tissue type based on the pictures taken during a mammogram. To determine breast density, the radiologist will compare the relative amounts of supportive or glandular tissue (which appears white or dense on the mammogram) and fatty tissue (which appears black or non-dense on the mammogram). The breast density category reported on each mammogram only takes into consideration the appearance of the breast on the mammogram pictures; it does not take into account what the breast may look or feel like on physical exam. There are four categories of breast density according to the American College or Radiology: Fatty (A), Scattered Fibroglandular (B), Heterogeneously Dense (C), and Extremely Dense (D). All breast densities are considered to be completely normal.

  • Fatty (A) or Scattered Fibroglandular (B) — In breasts that are considered Fatty or Scattered Fibroglandular in density, there is more fatty tissue than supportive tissue in the breasts.
  • Heterogeneously Dense (C) or Extremely Dense (D) — In breasts that are considered Heterogeneously Dense or Extremely Dense, there is more supportive tissue than fatty tissue in the breasts.
    • Heterogeneously dense indicates there is some fatty (non-dense) tissue in the breasts, but most of the tissue is supportive (dense). About 40% of women have heterogeneously dense breasts.
    • Extremely dense indicates that almost all of the tissue in the breasts is supportive and there is very little fatty tissue. About 10% of women have extremely dense breasts.

According to the new state mandate, women with breasts classified as either heterogeneously dense or extremely dense are required to be notified of the potential for increased masking of breast malignancies and of the potential for increase in breast cancer risk with denser breast tissue.

Can breast density change?

Yes! There are many factors that can contribute to changes in breast density from year to year. Changes in a patient's weight, menopausal or hormonal status, and many other factors can all contribute to variations in the relative amounts of the different types of breast tissue. Although most of the time breast density remains relatively similar from year-to-year it is not unusual for there to occasionally be changes to an individual's reported breast density.

Who is more likely to have dense breasts?

Some factors that may increase the likelihood of dense breasts include:

  • Younger age
  • Premenopausal
  • Using hormone therapy to help with menopause

Why is it important to for patient to know their breast density?

Patients can make an informed decision when considering screening for breast cancers when they know the density of their breasts. High breast density can make it more difficult to screen for breast cancer during a mammogram and may contribute to increased risk for breast cancer in women according to some studies.

In November 2017, the American College of Radiology (ACR) updated its recommendations regarding breast cancer screening. Annual mammography remains the gold standard for breast cancer screening for women 40 years old and older, regardless of breast density, with the ACR Appropriateness criteria giving screening mammography with 3D tomosynthesis imaging it's highest rating of “usually appropriate”. In fact, mammography is the only test that we have that has been proven to reduce death and complications related to breast cancer.

Regardless of breast density, women with a high lifetime risk of malignancy (>20%), should consider supplemental screening with yearly breast MRI in addition to annual screening mammography.

For women of average to intermediate lifetime risk of breast cancer, the ACR states that adding screening breast ultrasound to the screening regimen “may be appropriate”. Women with dense breast tissue are encouraged to discuss the risks and benefits associated with adding screening breast ultrasound to their breast cancer screening program. Though screening breast ultrasound has been shown to slightly increase the rate of cancer detection when used in conjunction with screening mammography with tomosynthesis imaging (by about 0.2%), it is not a very specific test and there is a high likelihood of being recalled for additional imaging. Additionally, approximately 10% of women who undergo screening breast ultrasound will ultimately be recommended to undergo biopsy.

What is 3D tomosynthesis imaging?

3D mammography converts digital breast images into a stack of very thin layers to build a three dimensional mammogram. 3D mammography increases the ability to detect cancer; in fact, some studies report an increase in detection of small invasive cancers by up to 40% with the addition of 3D mammography. Though all women can benefit from 3D mammography, some studies suggest those with denser breast tissue have the potential for greater benefit because dense breast tissue can cover up or make it harder to see cancers. Though 3D mammography decreases the chance of getting recalled, there are still follow up screenings when necessary. In the last year, many insurance companies have started covering 3D mammography.

Visit The Iowa Clinic Medical Imaging Department or call 515.244.5109 for more questions.

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