As a primary care physician, a good part of my day is spent navigating cancer screening with patients. One topic in particular that comes up on a daily basis is the appropriate type of breast cancer screening for women that have high density breast tissue. Keep reading to learn about what it means to have high density breast tissue, why it’s significant and how it impacts your risk for breast cancer.

What does it mean to have high density breasts?

Spoiler alert- it has nothing to do with how well-endowed you are.

High density breast tissue refers to the way different parts of the breast appear to a radiologist when reading a mammogram. High density is an imaging term and cannot be diagnosed clinically with a breast exam or otherwise, meaning it has nothing to do with size.

Let’s start with breast composition- all breast tissue is composed of fat, milk glands, milk ducts and supportive tissue. The glands, ducts and supportive tissues appear to be white, or dense, on imaging, while fat looks black or less dense. When reading mammograms, Radiologists use a grading system from 1-4 to quantify just how much of the breast is fat (black) tissue vs. “dense” (white) tissue.

Grade 1- Almost all fat- easier to see through- this will be the case for 1/10 women
Grade 2- Scattered areas of fibroglandular density”- still fairly easy to see through, some areas of density (concentrated white)- this will be the case for 4/10 women
Grade 3- Heterogeneously dense- most of the breast is dense (white), some black (fat)- this will be the case for 4/10 women
Grade 4- Extremely dense- very little fat, almost all breast tissue- this will be the case for 1/10 women

Grade-3 and 4 are considered dense breasts.

Why do I have dense breast tissue?

Younger patients tend to have denser breast tissue as well as those with lower BMIs (since they tend to have less fat everywhere) and finally, those taking combination HRT (hormone replacement therapy) for menopause.

Why is this relevant?

This is important for 2 reasons:

1) Breast cancer also appears white (dense) on mammograms, the thought is that in highly dense breast tissue, it may be more difficult to identify a breast cancer amongst all the other “white” density

2) More breast tissue, higher risk of breast cancer

How does this affect my risk for breast cancer?

High density breast tissue increases the difficulty of detecting breast cancer (less contrast between tissue and cancer) as well as the risk conferred by the increased breast tissue itself.

Okay so what do I do about breast cancer screening? Should I be getting an annual MRI like the “high risk” patients?

This is where things are less clear. You should certainly continue with your annual mammography; with high density breast tissue it is probably best to get a 3D mammogram (digital breast tomosynthesis) due to the improved detection rate.

With respect to additional testing:

Breast MRI remains a recommendation for those with “very high breast cancer” risk, though it is unclear whether dense breast tissue alone would confer “very high risk” it is best to discuss this with your doctor.

Abbreviated MRI (fast MRI) fewer images than a traditional breast MRI, still uses contrast enhancement but is faster, and less expensive- it is currently being studied as a screening for breast CA detection, especially in those with high density breast tissue. I recently spoke with a medical breast oncologist who reports that preliminary data comparing fast MRI and traditional breast MRI are promising for the detection of breast cancer in high density breast tissue. Guidelines continue to support full MRI for screening in patients with a high risk of breast cancer.

Breast US this is generally done to look at areas that are suspicious on mammogram- it can help the radiologist detect differences between solid and fluid filled masses- cancers are typically solid.

Dense breast tissue does increase the risk of breast cancer; however, it does not increase the risk of breast cancer related mortality.

Talk to your doctor for more information about which screening tests are right for you.

Sincerely,
Corsano MD- your friendly neighborhood PCP

Mayo clinic, American College of Obstetrics and Gynecology (ACOG)
Image: Breast Density: Understanding its Significance and Impact on Breast Health | Consulting Radiologists