Some women have more fibrous tissue in their breasts than they do fatty tissue. When a woman has a high proportion of fibrous tissue, a doctor may diagnose her with dense breasts.
It is important that women are aware of the density of their breasts because denser breasts can make cancerous lesions more difficult for doctors to identify.
- Having dense breasts is not uncommon.
- Doctors will diagnose dense breast tissue using an imaging scan known as a mammogram.
- Sometimes, medications can affect a woman's breast density.
- As a general rule, a woman's breasts will become less dense over time.
What is dense breast tissue?
Mammogram showing dense breasts (left) and fatty breasts (right).
Image credit: Dr. Kathy Cho, National Institutes of Health, 1994
Breast density is measured by the amount of fatty tissue in the breasts. The more fatty tissue, the less dense the breasts are.
According to some statistics, an estimated 40-50 percent of women aged 40-74 have dense breasts.
Women with dense breasts are more likely to have false-negative mammograms than women who do not have dense breasts, according to the National Cancer Institute. Recent research studies have also linked dense breasts to an increased risk of having breast cancer in both breasts.
While having dense breasts in no way guarantees a woman will get breast cancer, it is known to be a contributory factor and doctors are trying to define its relationship to breast cancer further.
A common misconception about dense breasts is that they are firm or large. However, a woman with firm breasts does not necessarily have dense breasts. The density of a woman's breasts can change over time. For example, as a woman ages, hormonal changes may cause more fatty tissue to develop in her breast.
Risk factors for dense breast tissue may include younger women and a family history of dense breast.
There are several risk facts including:
- Age: The younger a woman is, the denser her breasts tend to be. Older women typically have less dense breasts.
- Medication: Women who take hormone replacement therapy after menopause may see an increase in their breast density.
- Genetics: Women with dense breasts are more likely to have mothers and grandmothers with dense breasts too.
Doctors suggest that dense breast tissue is usually genetic.
Doctors can only detect dense breasts by looking at an X-ray or another imaging study. Usually, women will have a mammogram. A mammogram is an X-ray of the breast that allows a doctor to identify potentially cancerous lesions as well as dense breast tissue.
Doctors will divide breast tissue into four categories:
- mostly fatty
- scattered density
- consistent density
- extremely dense
While a doctor may separate breast tissue into these four categories, there is no formula that can place a woman in any of them.
Typically, the fatty breast tissue will appear dark on an X-ray, and cancerous lesions will appear white.
However, breast tissue that is very dense will also appear white on the X-ray. This similarity in appearance can make identifying potentially cancerous lesions more difficult.
It is also possible that a doctor might diagnose a particularly dense area of tissue as a tumor only to find that it is, in fact, an area of increased breast density.
Different imaging techniques, such as MRI scans, may be required to accurately diagnose dense breast tissue or tumors. Occasionally, X-rays or mammograms may not detect all abnormal tissue. In this case, alternate imaging techniques should be considered.
Sometimes, a doctor may recommend an ultrasound. Ultrasound uses sound waves and can help a radiologist detect if a lump is solid or fluid-filled.
Breast tomosynthesis uses 3-D imaging to recreate the breast.
Dense breast tissue cannot be prevented, but refraining from smoking and limiting alcohol may help to reduce the risk of breast cancer.
While there are no ways to prevent dense breast tissue from developing, a woman can engage in lifestyle choices that help her to reduce her risk for breast cancer.
- maintaining a healthy weight
- engaging in regular physical activity
- refraining from smoking
- limiting alcohol intake
Guidelines recommend no more than one drink per day for most women.
Researchers have not identified whether taking medications to reduce breast density will decrease a woman's breast cancer risk.
A doctor will likely consider a woman's additional risks for breast cancer and recommend imaging frequency. For example, if a woman has dense breasts as well as a family history of breast cancer, she may require more frequent imaging scans.
Is there a cancer link?
Women with dense breasts are associated with a higher risk for breast cancer.
According to an article in the Journal of the National Cancer Institute, women with dense breast tissue are 4-5 times more likely to get breast cancer than women who do not.
Another study published in the journal Cancer found that women with dense breasts who have breast cancer in one breast are at greater risk for developing breast cancer in the opposite breast.
This knowledge may help doctors counsel women regarding detection of breast cancer as well as treatment approaches for those women who have cancer.
More than 20 states have passed laws requiring radiologists to inform all the women that they have identified as having dense breasts so that they can be aware of their increased risk. If a woman receives this information, she should discuss it with her doctor.
If a woman is identified as having dense breasts, she should talk to her doctor about her individual risks for breast cancer given her health and family history.
A woman and her doctor can plan a screening schedule, if needed, or arrange additional imaging scans to further evaluate her breasts.
The American Cancer Society recommend women ages 45-54 get a mammogram each year. After age 55, some women may switch to screenings every 2 years, should they choose to do so.
Women with a family history of breast cancer or who wish to begin screenings earlier can talk to their doctor about doing so.