What Are Dense Breasts?

Breast tissue is composed of dense fibroglandular tissue (milk glands and ducts, muscle and connective tissue) and non-dense fatty tissue. The more fibroglandular tissue you have, the denser your breasts are. Dense breast tissue is very common and not abnormal. However, dense breast tissue is associated with an increased risk of developing breast cancer and, in addition, makes breast cancer screening
more difficult.

Nearly half of all women age 40 and older who have mammograms are found to have dense breasts (either heterogeneously or extremely dense). Women with 50 percent or higher breast density are three times more likely to be diagnosed with breast cancer than women with less than 10 percent breast density (Journal of the National Cancer Institute, Aug 2011).

Breast density is not based on how your breasts feel, and is not related to breast size or firmness. Breast density can only be determined with a mammogram. All Princeton Radiology SmartMammTM (mammogram) reports include your type of breast density, along with your lifetime risk assessment of breast cancer – to help you and your doctor determine the right monitoring plan for you.

Mammograms are the gold standard for breast cancer screening. The enhanced early detection capabilities of 3D mammograms benefit all women, especially those with dense breasts. However, some early-stage cancers are more difficult to detect on mammograms alone. That is because dense breast tissue appears white on a mammogram and nodules (both benign and cancerous) also appear white.


Dense breasts have more fibroglandular tissue. The chart below shows the four categories of density.

Type A
Almost Entirely Fatty

Type B
Scattered Areas of Fibroglandular Density

Type C
Heterogeneously Dense

Type D
Extremely Dense


Breast MRI is a painless imaging exam without ionizing radiation. Patients lie face down in the MRI machine, while an extremely safe contrast agent is typically administered intravenously. The MRI machine then uses magnets and radio waves to produce detailed 3-dimensional images of the breast tissue.

On the breast MRI, the intravenous contrast agent becomes more concentrated in areas of cancer growth, showing up as white areas against a dark background. This helps radiologists determine which areas may be of concern.

Women with dense breasts can benefit from supplemental screening with one of Princeton Radiology’s Smart Breast MRIs.™ Smart Breast MRI™ can detect more than twice as many breast cancers as 3-D mammography alone – and often at earlier, more treatable stages.

Types of Smart Breast MRI™ Exams

Princeton Radiology offers both Diagnostic and Smart Screen Breast MRI.™ Most insurance plans cover Diagnostic Smart Breast MRI for women at increased risk of developing breast cancer, such as those with a Claus risk score of 20+ on their SmartMamm™ report, and/or an inherited conditions such as BRCA 1 or BRCA 2 genetic mutations. If a Diagnostic Smart Breast MRI™ exam is not covered by your insurance, our Smart Screen Breast MRI™ is available for the low, self-pay fee of $375.

Diagnostic Smart Breast MRI™

  • Diagnostic breast MRI exam protocol with injected contrast
  • Exam time: approx. 30 minutes
  • May be recommended as a follow up to a SmartMamm™
  • Recommended if you have an average risk of breast cancer, but have concerns due to family history or other reasons
  • A physician prescription is required

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Smart Screen Breast MRI™

  • Screening breast MRI protocol
  • Uses injected contrast and selective image acquisitions shown to be more effective in finding lesions than mammography alone
  • Exam time: approx. 10 minutes
  • Recommended for concerned patients and their doctors when referral for diagnostic breast MRI does not meet insurance coverage requirements
  • Not covered by most insurance plans; out-of-pocket cost: $375
  • A physician prescription is required

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Additional reasons to consider a Diagnostic Smart Breast MRI™ include:

  • General concerns about breast health and risk factors not resolved with a mammogram
  • Discovery of a lump/mass during a physical exam, ultrasound or mammogram
  • Concerns about the integrity of breast implants
  • Distinguishing between scar tissue and recurrent tumors
  • Staging of breast cancer to make the best treatment decisions

Additional reasons to consider a Smart Screen Breast MRI™ include:

  • If you have an average risk of breast cancer but have concerns due to family history or other reasons
  • Additional safety net that detects 15 to 18 more breast cancers per 1,000 screenings
  • Ability to reveal aggressive cancers, as it detects tumors that are vascular and can grow quickly in between annual mammograms
  • Is radiation-free and painless


A small percentage of breast MRIs require additional testing. These might include a follow-up diagnostic Smart Breast MRI™, breast ultrasound, diagnostic SmartMamm™ (mammogram), or biopsy.


Yes! Even with dense breasts, mammograms are the only imaging exam proven to reduce breast cancer mortality. Mammograms also help detect changes in the pattern of your breast density, which is critical for detecting breast cancer early. We recommend that you continue with annual mammograms.