Breast Density: Does it matters?

If you have had a recent mammogram and the report mentions normal findings but an increased breast density, you may be a bit confused. Don’t worry! I am going to give you a little insight into what breast density is and what is important for you to know.

Firstly, it has nothing to do with how your breasts feel. Breast density simply refers to the appearance of breast tissue on a mammogram. Breasts are made up of fatty tissue (appears dark on mammograms) and glandular tissue (appears white on mammograms). Every woman has a different proportion of fatty versus glandular tissue in their breasts. Also, younger women tend to have dense breasts compared to older women. If your mother had dense breasts, it is possible you may too. As women age, their breasts tend to become fatty, especially after menopause.

So why must you be concerned about breast density?

Firstly, dense breasts are harder to read on a routine mammogram. You must know that cancers typically appear white on mammograms just as glandular tissue does. Therefore, more the glandular tissue (appears white) on the mammogram, the higher is the chance for a cancer (also appears white) to be obscured or masked by it! That is why additional imaging tests are recommended to supplement screening mammography.

Secondly, it has been reported that there is a two- to six-fold increase in the risk of breast cancer in women with dense breast tissue compared with those with a fatty pattern. This means that increased breast density is an independent risk factor for breast cancer. The degree of increased risk is lesser than major risk factors such as age, family history, and genetic mutations.

In the United States, 36 states have passed density notification laws to achieve uniformity in breast density reporting. This was a result of the relentless efforts of Miss Nancy Capello, who was herself diagnosed with breast cancer which was missed on her prior screening mammograms
due to her dense breast tissues. Nancy ardently fought for and managed to achieve the passing of the breast density notification laws across the United States and laid the foundation of to educate people about breast density and the need to advocate change in policy.

Despite concerns about detecting cancer in dense breasts, mammograms are still the most effective screening tools and the best way to detect breast cancer. Studies have shown that radiologists may not see 15-20% of cancers on a 2D digital screening mammogram due to which additional breast cancer screening tests may be warranted in women with dense breast tissues. Although no tests are 100%sensitive in detecting breast cancer, multiple imaging options are available for additional screening.

Besides opting for a full-field digital mammogram (2D), a recent imaging technology namely tomosynthesis (3D mammography) is of value in dense breasts. Tomosynthesis takes several pictures of your breasts, reduces tissue overlap and increases cancer detection rates, potentially revealing cancers that would have otherwise been missed. In fact, 3D Mammograms detect 1-3 more cancers per 1000 patients as compared to 2D Mammograms. They also result in fewer call backs for additional imaging compared with 2D mammography because this technology reduces tissue overlap and enables the radiologist to differentiate between dense breast tissue and a developing cancer more accurately.

In women with dense breasts, whole breast ultrasound may be performed by a radiologist in conjunction with the mammogram. Ultrasounds detect 2-3 more cancers per 1000 patients compared to 2D mammograms. This test is performed by the radiologist who has read your mammogram. Breast MRI is another sensitive modality and detects 8 more cancers per 1000 patients compared with 2D mammography and is often used as adjunctively for screening high- risk patients.

However, no single breast imaging screening tool is perfect. Based on recommendations by the American College of Radiology, Society of Breast Imaging, if you are at an average or low risk for developing breast cancer (lifetime risk of <15%), just a routine screening with a yearly 3D screening mammogram should suffice. If you are at intermediate risk for developing breast cancer (lifetime risk of 15-20%) supplemental screening with whole breast ultrasound or MRI can be considered after discussion with your referring physician. However, as mentioned earlier, if you are at a high risk for developing breast cancer (lifetime risk of >20%) supplemental screening is recommended.

Understanding what breast density is, as well as knowing your individual risk for developing breast cancer, will allow you and your doctor to make an informed choice regarding supplemental breast screening.

Remember, breast density is not something you can control, but knowing that you have dense breasts makes you more aware of what the risk is. When you schedule your mammogram, enquire whether your clinic offers a 3D mammogram and ultrasound facility. Speak with your breast radiologist about your breast density and its implications. Be breast aware. Early detection matters!

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