A SYSTEMATIC REVIEW DISCOVERED THAT EXTREMELY DENSE breast tissue is associated with doubling breast cancer risk. This risk estimate is lower than offered in previous studies. Today we explore why breast density matters.
Breast density on mammograms is a well-defined risk factor for breast cancer. Some studies show an up to a six-fold increase in the chances of getting breast cancer.
Does this risk estimate apply to current breast density classification methods? Researchers aimed to clarify the density and breast cancer link.
What is breast density?
Breast density measures how much fibrous and glandular tissue (fibroglandular tissue) is in your breast compared to fat tissue. Breast density has nothing to do with breast size or firmness.
The breast is composed of milk ducts, lobules, and fatty and fibrous connective tissue. The fibrous tissue and fat give breasts their shape and size while holding other structures in place.
- Lobules are tiny milk-producing glands, while ducts are the small tubes that can carry breast milk from the lobules to the nipple.
- Fibrous tissue and fat determine the size and shape of the breast while holding other structures in place.
It is more challenging to see fibrous and glandular tissue on a mammogram, so the breast tissue may be called dense if you have a lot of fibrogandular tissue (and relatively less fat).
Dense breast tissue is common, but breast density decreases with age for most (but not all) women.
How do you know if you have dense breasts?
A radiologist is a doctor who “reads” your imaging studies, including mammograms. They examine your mammograms for abnormal areas and also measure breast density.
The BI-RADS (Breast Imaging Reporting & Data System) atlas provides standardized breast imaging terminology, imaging report terminology, and a classification system for breast imaging.
The classification scheme conveniently divides breast density into four categories, ranging from almost all fatty tissue to extremely dense tissue with very little fat.
- Category A: Breasts are almost all fatty tissue.
- Category B: Scattered areas of dense glandular and fibrous tissue (seen as white areas on the mammogram).
- Category C: More of the breast is made of dense glandular and fibrous tissue (described as heterogeneously dense). This density can make it hard to see small masses in or around the dense tissue, which also appear as white areas.
- Category D: Breasts are extremely dense, which makes it harder to see masses or other findings that may appear as white areas on the mammogram.
What percentage of women have dense breasts?
The breasts are almost entirely fatty (about 10 percent of women). For another 40 percent, a few areas of dense tissue are scattered through the breasts. The breasts are evenly dense for approximately 40 percent of women. Finally, about 10 percent of women have extremely dense breasts.
Women in categories A or B have low-density, non-dense, or fatty breasts. Approximately half of the women will have either heterogeneously dense or extremely dense breasts (Categories C or D).
You are more likely to have dense breasts if you:
- Are younger
- Are pregnant or breastfeeding
- Are taking hormone replacement therapy
- Have a lower body weight
Why is breast density important
There are two important reasons why breast density is important. First, those with dense breasts have a higher chance of getting breast cancer. The more dense the breast, the higher the risk. However, those with dense breasts are not more likely to die from breast cancer.
Second, dense breast tissue can hide cancer. Fibroglandular tissue appears white on a mammogram. Cancer also appears white so that a small tumor can be missed.
The new study provides insights into the risk increase associated with breast density. Researchers examined nine observational studies, discovering the following:
After adjusting for age and body mass index, extremely dense breast tissue (BI-RADS density D) had a 1.8-fold increased breast cancer risk compared to those with scattered breast tissue (BI-RADS density B).
In summary, extreme breast density (BI-RADS D) is associated with a nearly two-fold increased breast cancer risk. This study is particularly valuable as it used modern digital imaging techniques and the latest BI-RADS lexicon.
If I have dense breasts, do I need a mammogram?
Yes. Most breast cancers are identifiable on mammograms, even if the breasts are dense. Mammograms still save lives.
There is no consensus on additional imaging for those with dense breasts. Digital breast tomosynthesis (3D mammography) can find some cancers not seen on regular (2D) mammograms. Some studies show that 3D mammograms are particularly helpful for those with dense breasts. Many imaging centers have 3D mammography.
For some, breast ultrasound and magnetic resonance imaging (MRI) are better at finding breast cancers not seen on mammograms. Ultrasound and MRI also have high false positive rates; the tests find a lot of abnormalities that turn out not to be cancer.
Your healthcare provider can guide whether additional imaging tests are indicated for you. Let your provider know if there is anything in your medical history that increases your breast cancer risk. To learn more about breast cancer risk factors, please go here:
Women with a very high breast cancer risk may have an MRI plus an annual mammogram.
The information I provided in this blog is for educational purposes only and does not substitute for professional medical advice. Please consult a medical professional or healthcare provider if you seek medical advice, diagnoses, or treatment. I am not liable for risks or issues associated with using or acting upon the information in this blog.
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