Dense Breasts and Cancer: What to Know About Katie Couric’s Diagnosis

On Wednesday, Katie Couric revealed that she had breast cancer. In an essay on her website, she wrote about the “heart-stopping, suspended animation feeling” she had upon receiving her diagnosis in June; she also noted that she had dense breasts — a common classification that can increase the risk of developing the disease.

About half of women who are 40 years old or older have dense breast tissue, said Dr. Laura Esserman, director of the Breast Care Center at the University of California, San Francisco. Here’s what to know about what breast density means and how dense breasts can influence cancer risk.

Density isn’t related to breast size or firmness, said Dr. Sarah Friedewald, chief of breast imaging at the Northwestern Feinberg School of Medicine. It is a measure of how much fibrous and glandular tissue is in your breasts compared with the amount of fatty tissue as viewed on a mammogram. These tissues include the glands that create milk, the tubes that ferry milk to the nipples and the fibrous tissue that binds them together.

Every mammogram report includes an assessment of a woman’s breast density, which falls into one of four categories: almost entirely fatty; some areas of scattered density; evenly dense; or extremely dense. Dense breasts is an umbrella term that refers to the latter two categories.

Scientists aren’t entirely sure why dense breasts increase the risk for cancer, Dr. Friedewald said, but the thick tissues make mammogram detection for calcifications and tumors more difficult.

While the majority of states require doctors to notify patients that they have dense breasts, not every state has that legislation, Dr. Esserman said.

If you get a mammogram and are not informed about your breast density, you should ask your doctor directly if you have dense breasts, said Dr. Elizabeth Comen, a medical oncologist at Memorial Sloan Kettering Cancer Center in New York City.

According to the Centers for Disease Control and Prevention, women who are younger, pregnant or breastfeeding, taking hormone replacement therapy, or who have a lower body weight are more likely to have dense breasts. But any woman at any age can have dense breasts, Dr. Come said.

The denser your breasts, the higher your risk for breast cancer. But breast density is just one of many risk factors, Dr. Esserman said, and having dense breasts is nowhere near a guarantee that you will develop the disease.

Age is the greatest risk for breast cancer, said Dr. William Dahut, chief scientific officer for the American Cancer Society. Family history and genetics also play a key role as do lifestyle factors like alcohol use or lack of exercise.

“Breast density in and of itself is not a huge risk factor,” Dr. Friedewald said. Dense breasts can make it more difficult for doctors to evaluate a mammogram, and so they may require additional imaging.

Screening guidelines for breast cancer do not differ depending on breast density, Dr. Dahut said. If you have an average risk of developing breast cancer — meaning you are not at heightened risk because of family history, genetics or other factors — you should get a mammogram each year starting at age 40. If you have dense breasts, you will likely still get screened on that cadence, Dr. Friedewald said, but you might also get additional imaging, like a breast ultrasound or magnetic resonance imaging. Consult with your doctor about the best screening plan for you. Online tools, like the Breast Cancer Surveillance Consortium Risk Calculator, can also help assess your risk.

Ms. Couric’s announcement is a helpful reminder of just how essential it is for everyone to be mindful of their cancer risk and to screen for it according to medical guidelines, experts said. Breast and cervical cancer screening declined sharply during the pandemic.

“Women are so often put in a position of caring for other people, especially in the pandemic,” Dr. Come said. “It’s so important that women have the space and time and support to take care of themselves.”