What Causes Dense Breast Tissue?

Here's what causes it and what to do if you have a higher-than-normal mammographic density.

Mammograms are a good way to detect breast cancer. Another finding exclusive to mammograms is dense breast tissue. With dense breast tissue, a lot of fibrous and glandular tissue appears white or light gray on the X-ray images. 

Tumors, or abnormal growths, can also appear white on a mammogram. So, having dense breast tissue can make it hard to detect breast cancer. Also, people with dense breast tissue have a higher risk of breast cancer than others. Although, the reasoning is unclear.

Here's what you should know about dense breast tissue, the factors that influence it, and how to screen for breast cancer properly.

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What Is Dense Breast Tissue?

Breasts are made up of three types of tissue, which include:

  • Fibrous connective tissue: This tissue helps hold the breast in place.
  • Glandular tissue: Also known as lobules and ducts, this tissue produces and stores breast milk. Lobules are glands that produce milk. Ducts are tiny tubes that carry milk from the lobules to the nipple. 
  • Fatty breast tissue: This tissue is interspersed between lobules and ducts.

Fibrous and glandular tissue are collectively known as dense tissue. So, dense breasts have more fibrous and glandular tissue in relation to the amount of fatty tissue.

Dense breast tissue is "tissue on the mammogram that is hard to see," Anita Johnson, MD, a surgical oncologist at the Cancer Treatment Centers of America, told Health.

To assess mammographic density, or the percentage of dense tissue in the breasts, healthcare providers use the Breast Imaging Reporting and Data System (BI-RADS). 

Using the BI-RADS, healthcare providers assign a score ranging from one to four. A mammographic density of level one indicates that the breast is composed almost completely of fatty tissue. In contrast, level 4 describes breasts with 75% or more dense tissue.

What Causes Dense Breast Tissue?

Sometimes, people inherit dense breast tissue. Other times, other factors can influence breast density. For example, post-menopausal hormone therapy may increase your risk of having dense breast tissue. Also, evidence suggests that people with a low body mass index (BMI) are more likely to have dense breasts than others.

Another important factor is age. Research has found that breast density decrease with age. The most significant changes in breast density happen during menopause. Therefore, people younger than 44 are more likely to have dense breast tissue than others.

Does Breast Density Affect Breast Cancer Risk?

In some cases, high breast density may link to an increased risk of breast cancer. For instance, dense breast tissue can reduce the sensitivity of a mammogram. It may be difficult for a healthcare provider to detect abnormalities when that happens. 

Also, a study published in 2020 in the International Journal of Cancer found that people with high breast density are more likely to have interval cancer. Interval cancer presents during the time between regular screenings. Therefore, prioritizing regular screenings is key to early detection and prevention.

What To Do if You Have Dense Breasts

Dense breast tissue is not something you can get rid of, explained Dr. Johnson. Although there's no treatment for dense breast tissue, X advises that people who are at risk for breast cancer and anyone above the age of 40 get routine mammograms.

Since breast density has the capability to obscure tumors, mammogram centers are obligated to inform people of their findings, which includes breast density.

Knowing if you have a higher mammographic density can help assess your risk of breast cancer. But keep in mind that not everyone who has dense breasts will develop cancer. 

Screening With Dense Tissue

As of January 2023, "there are no guidelines on what to do with the information on increased breast density. There are studies looking at whether 3-D mammography is better than 2-D in saving lives," explained Dr. Johnson. "But in most cases, ultrasound and breast MRI are recommended to further assess the situation."

The American College of Obstetricians and Gynecologists (ACOG) provides that mammograms are one of the most useful tools for detecting breast cancer. Also, the ACOG states that routine mammograms help reduce breast cancer mortality. When cancerous growths are found early, treatment is most effective.

Several guidelines mention that the decision to start getting regular mammograms between the ages of 40–49 is a personal choice. However, consider talking to a healthcare provider about regular screenings, especially if there's a family history of cancer, advised Dr. Johnson. 

A Quick Review

Dense breast tissue occurs when there's more fibrous and glandular tissue than fatty tissue. In some cases, having dense breasts links to an increased breast cancer risk. But remember that not everyone with dense breasts will develop breast cancer.

There's no treatment for dense breast tissue. However, getting regular mammograms and discussing your screening options with a healthcare provider can help detect and treat breast cancer early. 

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