Does having dense breasts increase the risk of cancer?

In 2023, breast cancer was the most diagnosed cancer among women in the United States. It was also one of the four types of cancer that contributed to approximately half of all deaths.

According to the Centers for Disease Control and Prevention, having dense breast tissue is a significant risk factor for breast cancer.

Breast density refers to the amount of fibrous and glandular breast tissue seen on mammograms compared to the amount of fatty breast tissue seen. Dense breasts are common, with mammograms classifying about 40% to 50% of women as having dense breasts.

“Dense breasts have a lot of glandular tissue — which includes the milk glands and ducts — and fibrous tissue,” says Dr. Lori Uyeno, a Sharp Community Medical Group breast surgeon affiliated with Sharp Memorial Hospital. “There’s not as much fatty tissue in dense breasts.”

Breast density is most often determined by mammogram imaging, Dr. Uyeno adds. It is not based on the human eye or touch.

Dense breast tissue and cancer diagnoses

When it comes to determining why having dense breasts increases the chances of getting breast cancer, researchers are still seeking concrete answers. Some theorize that dense breasts have more cells that can turn into cancerous cells with aging.

What’s more, dense breast tissue on mammograms can mask or hide small cancers. Dense breast tissue appears white, while fatty tissue appears black on mammograms. Breast cancer also appears white on mammograms, which can make detection difficult. “Yet, routine screening mammograms are still one of the best imaging options for detecting cancers, even in dense breasts,” says Dr. Uyeno.

Medical professionals can recommend additional imaging, such as tomosynthesis or 3D mammography when screening for breast cancer. This type of exam produces images taken as an arc to generate a 3D model of the breast for a more accurate reading.

“Other types of exams include ultrasounds or breast MRIs, which may be recommended for extremely dense breast tissue,” says Dr. Uyeno.

How age affects breast density

Breast density decreases with aging due to decreasing hormone levels. As such, older women have less dense breast compared to younger women. However, women who receive hormone replacement therapy for menopausal symptoms are more likely to have high breast density compared to women who are not receiving hormone replacement therapy.

“Hormone replacement therapy can be effective in relieving menopausal symptoms,” says Dr. Uyeno. “It’s important for women to discuss with their doctor about their personal risk of developing breast cancer before starting the therapy.”

Dr. Uyeno says it is important for all women to be vigilant and take note of any changes to breast skin, shape or size. “Also, look out for any nipple discharge or changes in how your breast feels and talk with your doctor if you have concerns,” she says.

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