On Cancer: Diagnostic Radiologist Carol Lee Discusses What Women Should Know about Breast Density

To help improve breast cancer detection and prevention, New York Governor Andrew Cuomo recently signed legislation that requires radiologists to inform women if dense breast tissue is found on a mammogram. The law, which went into effect this month, is raising awareness among women about this topic.

In an interview, we discussed the concept of breast density with diagnostic radiologist Carol H. Lee. Dr. Lee suggests that if you find out you have dense breasts, you should discuss potential next steps with your doctor. Each individual woman’s risk for breast cancer is different, and many factors – such as family history and lifestyle – must be taken into account when determining whether additional forms of breast cancer screening are necessary.

What are dense breasts?

Breasts are made up of different types of tissue: fatty, fibrous, and glandular. Fibrous and glandular tissues appear as white on a mammogram and fatty tissue shows up as dark. If most of the tissue on a mammogram is fibrous and/or glandular, the breasts are considered to be dense.

Because cancer cells also appear as white on a mammogram, it may be harder to identify the disease on a mammogram in women with dense breasts.

How common are dense breasts?

Breast density is classified into one of four categories, ranging from almost entirely fatty (level 1) to extremely dense (level 4). Dense breasts are completely normal. About half of all women have breasts that fall into the dense category (levels 3 and 4). Dense breasts tend to be more common in younger women and in women with smaller breasts, but anyone – regardless of age or breast size – can have dense breasts.

How does a woman know she has dense breasts?

The only way to determine whether a woman has dense breasts is with a mammogram. A breast exam cannot reliably tell whether a breast is dense.

What does having dense breasts do to a woman’s risk for breast cancer?

If you compare the 10 percent of women who have extremely dense breasts with the 10 percent of women who have very little breast density, the risk for breast cancer is higher in those with very dense breasts.

However, most women fall somewhere in between in terms of breast density, so it’s nearly impossible to determine whether a particular woman’s breast density is a risk factor for the disease.

What should women who are told they have dense breasts do?

Women found to have dense breasts should talk to their doctors about their individual risk for breast cancer and together decide whether additional screening makes sense.

Tests such as ultrasound or MRI can pick up some cancers that may be missed on a mammogram, but these methods also have disadvantages. Because they are highly sensitive, they may give a false-positive reading, resulting in the need for additional testing or biopsy that turns out to be unnecessary. There is also no evidence to show that using screening tests other than mammography in women with dense breasts decreases the risk of death from breast cancer.

Ultimately, women who have dense breasts should weigh the pros and cons of additional screening with their doctor.

Should women who do not have dense breasts make any changes to their regular screenings?

Women who do not have dense breasts may still develop breast cancer, and should continue to receive regular mammograms. Regular mammography is the only screening method that has been shown to decrease deaths from breast cancer, and all women of appropriate age should have mammograms, regardless of their breast density.

Memorial Sloan-Kettering provides comprehensive, individualized breast cancer screening services that include mammography, ultrasound, and MRI, through our Breast Screening Program, located in Manhattan.