f you are one of the many women who have dense breasts, you might have questions about what that means when it comes to breast cancer screenings and breast cancer risk.

Dr. Terese Kaske, a breast radiologist at UCHealth Gloria Gossard Breast Care Center, answers those questions and more, below.

What are dense breasts? 

Breasts that are composed mostly of fat are non-dense, while breasts that have more non-fatty tissue, including glands, ducts and fibrous tissues, are considered dense.

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Why do some women have dense breasts? 

About 40% of women in the U.S. have dense breasts, while in Steamboat Springs, that number reaches up to 50%. Breast density is largely determined by genetics, though losing or gaining weight may also impact relative density.

Do dense breasts feel different? 

No.

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“That’s a big misconception,” Kaske said. “Breast density is established by mammography.”

Non-dense or fatty breasts can feel very firm. And women who are thin can still have fatty breasts.

Your radiologist will provide information on your breast density every time you have a mammogram.

Can breast density change? 

Yes. As women age, hormone decreases may cause decreases in the glandular tissue in breasts.

And if a woman gains weight, she will usually gain fat in her breasts, which can result in a relative decrease in breast density. The reverse is also true: a woman who loses weight may lose fatty tissue in her breasts, resulting in a relative increase in breast density.

Why does breast density matter? 

It can be more difficult to spot cancer in dense breasts using mammography alone.

Cancer appears as a whiter area on a mammogram because it absorbs more X-rays. Fatty tissue, which allows more X-rays to pass through, appears darker gray, so cancers stand out in imaging of a non-dense breast. But the extra fibroglandular and ductal tissue in dense breasts is also white or light gray, making it more difficult to see a cancer.

“We love fatty tissue, as you can see through the tissues,” Kaske said. “A technologist once said that fat is like a clear sunny day – you can see for miles. But the more dense a breast is, the more cloudy, smoky and hazy the sky is. The more dense, the more things can be masked.”

Are additional screenings recommended for women with dense breasts? 

Yes.

“For women with dense breasts, having a normal or negative mammogram does not exclude the presence of breast cancer,” Kaske said.

Women with dense breasts who are at high risk for breast cancer due to family or personal history will likely need a breast MRI, while women with dense breasts who are at average risk can benefit from a screening breast ultrasound in addition to a mammogram.

“Ultrasound is very good and has been proven to pick up additional cancers,” Kaske said. “But an ultrasound does not replace your mammogram – you need to have both. Mammograms, even in women with dense breast tissue, can find a cancer that an ultrasound can miss.”

That’s because many cancers present with small flecks of calcium, known as microcalcifications, that are easy to see on a mammogram, but not on an ultrasound.

Does having dense breasts increase breast cancer risk? 

Yes. Cancer starts in breast tissues, and denser breasts have more breast tissue. Having higher density breasts can increase your risk of breast cancer by up to four- or six-fold. Denser breast tissue can also increase risk of recall rates and of later breast cancer diagnoses.

Should I worry about getting a mammogram? 

No. As technology has advanced, the amount of radiation used in a mammogram has decreased significantly.

“Mammography has progressed so much, the radiation used is a very low dose,” Kaske said. “Mammograms are the only imaging examination to have undergone extensive study and randomized controlled trials to prove a mortality benefit – they find early breast cancers and save lives. Don’t be afraid of your mammogram.”

For more information, Kaske recommends densebreast-info.org.

Susan Cunningham writes for UCHealth Yampa Valley Medical Center. She can be reached at cunninghamsbc@gmail.com.