There is one known breast cancer risk factor that still raises a lot of questions: breast density.  About 10% of women have extremely dense breasts, and research has shown that their risk of developing breast cancer is double compared to those with non-dense breasts. While we can’t change our breast density, learning more about it empowers us to discuss appropriate screening strategies with our healthcare providers.

Your breasts are made up of different types of tissue: fatty tissue, and fibroglandular tissue (which includes milk-producing ducts, lobulesThe place within the breast where milk is manufactured in the breast., and connective tissue). Breast density refers to the proportion of these tissues. A dense breast has a higher amount of fibroglandular tissue compared to fatty tissue. Conversely, less dense breasts have a higher proportion of fatty tissue.

Research has consistently shown a link between breast density and an increased risk of breast cancer. Women with very dense breasts have a higher risk of developing breast cancer compared to women with less dense breasts.

Specifically, women with extremely dense breasts have a two times higher risk of developing breast cancer compared to women with almost entirely fatty breasts. While the exact mechanisms behind this increased risk are still being investigated, this is a significant difference that warrants attention.

Breast density is influenced by a combination of factors, many of which are beyond our control:

• • Genetics: Breast density often runs in families, suggesting a geneticInherited characteristics. predisposition.
  • Age: Breast density tends to decrease with age, particularly after menopauseThe end of a woman’s menstrual cycles, defined as 12 consecutive months of no menstrual periods..
  • Hormonal Factors:
    • • Pregnancy and Childbearing: Women who have had several children often experience a decrease in breast density.
      • Menopause: The hormonal changes associated with menopause typically lead to a decrease in breast density as fibroglandular tissue is replaced by fat.
      • Hormone Replacement Therapy (HRT): Postmenopausal hormoneA chemical substance produced in the body that controls and regulates the activity of certain cells or organs. therapy, particularly regimens involving estrogenA female sex hormone that is primarily produced by the ovaries. Its primary function is to regulate the menstrual cycle and assist in the production of secondary sex characteristics such as breasts. It may even play a role in the production of cancer cells in the breast tissue., can slow down this decrease in density and, in some cases, even increase breast density.

MammogramsA low dose x-ray picture of the breast that allows a doctor to view glandular tissue and determine the presence of cancer. depict our breast tissue in black, white and gray. Breast density can make it more challenging for radiologists to interpret mammograms accurately. This is because:

• • Fibroglandular tissue appears white on a mammogram, similar to how non-cancerous and cancerous masses would appear. This “masking effect” can make it difficult to distinguish between normal dense tissue and cancerous growths. This is similar to finding a polar bear (cancer) in a blizzard (dense white tissue).
  • Fatty tissue appears dark (black) on a mammogram, providing a clearer contrast for any abnormalities which appear white. This is why having more fatty tissue in your breasts (despite obesity being a risk factor for breast cancer overall) can actually improve the visibility of tumors on a mammogram.

The only way to know your breast density is through a mammogram or other breast imaging process. A radiologist will assess your breast density based on the appearance of your breast tissue on the image.

As of September 2024, the Mammography Quality Standards Act now requires all medical providers in the United States offering screening mammography to notify doctors and patients about breast density. The patient summary for those with dense breast tissue will include the following verbiage: Your breast tissue is dense. In some people with dense tissue, other imaging tests in addition to a mammogram may help find cancers. Talk to your healthcare provider about breast density, risks for breast cancer, and your individual situation.” This aims to empower women with important information about their breast health and provides an opportunity to discuss whether breast ultrasound or MRI is appropriate with their physician.

If you have dense breasts, discussing enhanced screening options with your doctor is crucial for early detection. These options may include:

• • 3D Mammography (Digital Breast Tomosynthesis – DBT): This mammography technique takes multiple images of the breast from different angles, creating a 3D reconstruction. This can help radiologists see through dense tissue more clearly and reduce the masking effect.
  • Breast Ultrasound: Often used as a supplemental screening tool for women with dense breasts, ultrasound can help detect cancers that might be hidden on a mammogram.
  • Breast MRI (Magnetic Resonance Imaging): For women with dense breasts and other elevated risk factorsAnything that increases or decreases a person’s chance of developing a disease., an MRI may be recommended as an additional screening tool, as it is highly sensitive in detecting breast cancers.
  • Clinical Breast Exams: Regular clinical breast exams performed by a healthcare professional remain an important part of breast health monitoring.
  • Breast Self-Awareness: While not a substitute for professional screening, being familiar with your own breasts and promptly reporting any changes to your doctor is always recommended.

Remember, early detection is key in the fight against breast cancer. Knowing your breast density is a vital piece of information that can guide you and your doctor in developing the most effective screening plan for your individual needs.