The breasts consist of three main components: lobules, ducts, and connective tissue, which can be both fatty and fibrous. Some people have more fibrous than fatty tissue in their breasts. Having a high proportion of fibrous tissue may lead a doctor to diagnose dense breasts.

It is important that people are aware of the density of their breasts. Denser breasts can make cancerous lesions more difficult for doctors to identify.

In this article, we explain how dense breast tissue can interfere with breast cancer diagnosis and how to reduce the risk of breast cancer.

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High breast density means that a person has more fibrous tissue than fatty tissue in the breast.

The ratio of fatty tissue to fibrous, or dense, tissue in the breasts determines if a person has dense breasts. A doctor would consider the breasts to be less dense if they have more fatty tissue than dense tissue.

According to a study in the Journal of the National Cancer Institute, an estimated 43.3% of women ages 40–74 years have dense breasts.

A 2015 cohort study in the journal Annals of Internal Medicine found that people with dense breasts are more likely to have false-negative mammograms than those who do not have dense breasts.

Having dense breasts is related to a higher risk of breast cancer. However, doctors and researchers still do not understand why. Research is ongoing.

A common misconception about dense breasts is that they are firm or large.

However, people with firm breasts do not necessarily have dense breasts. Breast density can also change over time.

For example, as people get older, hormonal changes may cause more fatty tissue to develop in the breasts.

There are several risk factors associated with dense breast tissue, including:

  • Age: A 2018 study in the journal Cancer Epidemiology, Biomarkers and Prevention found that younger females tend to have higher breast density. Older females typically have less dense breasts.
  • Medication: Females who use hormone replacement therapy after menopause may see an increase in breast density, according to a 2018 cohort study in the journal Cancer Causes and Control.
  • Genetics: According to the National Cancer Institute, people often inherit dense breast tissue.

High breast density is associated with a higher risk of breast cancer.

A 2018 research study in the journal Radiology also linked dense breasts to an increased overall risk of breast cancer.

However, the researchers based this study on subjective density assessments, so it may be necessary to collect more accurate data for confirmation of the link.

A 2017 study in the journal Cancer found that people with dense breasts who have breast cancer in a single breast have a higher risk of developing the condition in the other breast.

Knowing this may help doctors counsel people regarding breast cancer detection and treatment approaches.

More than 20 states have now passed laws requiring radiologists to inform people of a diagnosis of dense breasts, so that they can be aware of their increased cancer risk.

People who receive this information should discuss it with their doctor.

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An MRI scan is another option for scanning dense breast tissue, but it may produce a false-positive result.

Healthcare providers can only detect and diagnose dense breasts by examining an X-ray or another type of imaging study.

Usually, people will have a mammogram. A mammogram is an X-ray of the breast that allows a doctor to identify potentially cancerous lesions in any dense breast tissue.

Doctors will use four categories to rank breast tissue density:

  • mostly fatty
  • scattered density
  • consistent density
  • extremely dense

Although a doctor may separate breast tissue into these four categories, there are no set criteria for ranking breast tissue density.

Typically, fatty breast tissue will appear dark on an X-ray, while cancerous lesions will appear white.

However, extremely dense breast tissue will also appear as white on the X-ray. This similarity in appearance can make it more difficult to identify potentially cancerous lesions.

It is also possible that a doctor might diagnose a particularly dense area of tissue as a tumor, then find in later scans that it is an area with increased density.

Different imaging techniques, such as MRI scans, may be necessary for accurately determining whether the highlighted tissue in the mammogram is dense breast tissue or a tumor.

Sometimes, X-rays and mammograms do not detect all abnormal tissue. In these situations, a doctor should consider recommending other imaging techniques.

For example, they may suggest an ultrasound. Ultrasound uses sound waves to create images of the breast and can help a radiologist determine whether a lump is solid or fluid filled.

Breast tomosynthesis is another option. It uses 3D imaging to recreate the breast.

Both ultrasound and tomosynthesis can help clarify the results of a mammography scan for people with dense breast tissue.

A breast MRI is another imaging option. Due to its cost and the higher likelihood of receiving a false-positive result, doctors will mainly suggest MRI scans for those who have a higher-than-average lifetime risk of breast cancer.

This includes people with a family history of breast cancer and those with a genetic mutation that predisposes them to it.

There are no methods available for preventing the development of dense breast tissue.

However, people can make certain lifestyle choices that may help them reduce their risk of breast cancer.

Examples include:

  • maintaining a healthy weight
  • engaging in regular physical activity
  • refraining from smoking
  • limiting their alcohol intake

Guidelines recommend no more than one drink per day for most women.

A doctor will likely consider a person's additional risk factors for breast cancer and recommend how often to receive screenings.

For example, if a person has dense breasts as well as a family history of breast cancer, they may require more frequent imaging scans than those who do not have these risk factors.

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Dense breasts increase the risk of cancer, but early detection through screenings means that a person with breast cancer has a very good outlook.

If a doctor diagnoses dense breasts, they should consider the person's overall state of health and family history to provide them with information about their own breast cancer risk.

People should work with their doctor to plan a screening schedule, if needed, or to arrange additional imaging scans.

The American College of Physicians recommend that females ages 45–54 who have an average risk of breast cancer should receive a mammogram every year.

However, those of average risk can choose to start annual screenings from 40 years of age onward.

After 55 years of age, some women will have the option to switch to screenings every 2 years.

The American Cancer Society advise differently. They recommend that people have the option to start annual screening at 40 years of age but should start by 45 years. They could then choose to move screenings to every second year by 55 years of age.

The American College of Radiology have different guidelines. They recommend yearly scans from 40 years of age.

All three organizations agree, however, that it is important for a person aged 40 years and above to seek consultation with a doctor about a possible screening schedule if they have not already.

Click here to learn more about breast cancer treatment and recovery.

Q:

Does dense breast tissue cause any other health problems?

A:

Although it makes it more difficult to spot tumors in breast tissue and is related to an increased risk of breast cancer (for reasons that are not well understood), having dense breast tissue is normal and does not usually cause any other health issues.

Yamini Ranchod, PhD, MS Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.