What is breast density, and how does it impact cancer risk?
By: Gaelyn Scuderi, M.D.
"I’ve been told I have dense breast tissue. What does this mean?” This is one of the most common questions my patients ask me. Breast density - and perhaps more importantly, the ramifications of having dense breast tissue - can be confusing topics for both patients and providers. But understanding the concept of breast density is very important, because your breast density may influence your individual breast cancer screening plan.
To understand breast density, you need to understand what kinds of tissues make up the breast. All breasts have basically two types of tissues: fatty tissue and glandular tissue. The glandular tissue is made up of hormonally responsive cells that perform the function of the breast: producing and secreting milk. The fatty tissues make up the remainder of the breast, and are not actively involved in milk production or secretion. The ratio of fatty tissue to glandular tissue is what determines each woman’s breast density. Women with more fatty tissue than glandular tissue are less dense, while women with a higher ratio of glandular tissue to fatty tissue are considered more dense.
Breast density is important because women with dense breasts (higher proportion of glandular tissue compared to fat) have a higher risk of breast cancer compared to women with low breast density (mostly fat). Breast density is therefore considered an independent risk factor for breast cancer.
Additionally, breast density can influence the interpretation of your mammogram. Women with high breast density have a more opaque appearance of their mammogram, sometimes making early signs of breast cancer difficult to detect. Because of this, women with dense breast tissues may require supplemental breast imaging tests in addition to the routine screening mammogram in order to fully exclude signs of early breast cancer. Some of these imaging studies may include digital breast tomosynthesis, diagnostic mammography, breast ultrasound, or breast MRI. Importantly, not all supplemental tests are appropriate for every woman. Each woman’s breast tissue pattern and individual risk factors are different, and not all patients with dense breasts require additional imaging. For all women, though, the fundamental first steps toward developing a personalized breast cancer screening plan start with talking to your doctor about your individual breast cancer risk, and undergoing regular screening mammography.