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Dense Breast Tissue Cancer Risk

How Common Are Dense Breasts

Mammogram Monday: Dense breast tissue can be a cancer warning sign

Nearly half of all women age 40 and older who get mammograms are found to have dense breasts. Breast density is often inherited, but other factors can influence it. Factors associated with lower breast density include increasing age, having children, and using tamoxifen. Factors associated with higher breast density include using postmenopausal hormone replacement therapy and having a low body mass index.

What Is Dense Breast Tissue

Breast density is a measure of how much fibrous and glandular tissue there is in your breast, as compared to fat tissue. It isnt related to breast size or firmness.

Breasts are made up of lobules, ducts, and fatty and fibrous connective tissue.

  • Lobules are the small glands that produce milk, while ducts are the tiny tubes that carry the milk from the lobules to the nipple. Together, the lobules and ducts are referred to as glandular tissue.
  • Fibrous tissue and fat give breasts their size and shape and hold the other structures in place.

Fibrous and glandular tissue are harder to see through on a mammogram, so your breast tissue may be called dense if you have a lot of these tissues .

Having dense breast tissue is common. Some women have more dense breast tissue than others. For most women, breasts become less dense with age. But in some women, theres little change.

What Are Researchers Hoping To Learn About The Relationship Between Breast Density And Breast Cancer

Some important questions include:

  • Can imaging tests such as 3-D mammography , MRI, and ultrasound help provide a clearer picture of breast density?
  • Are there certain patterns or areas of dense breast tissue that are particularly âriskyâ?
  • Why do some women with dense breasts go on to develop breast cancer, while others do not? Can biomarkers be identified that help predict whether breast cancer will develop in a woman with dense breasts?
  • Are changes in breast density over time associated with changes in breast cancer risk?
  • Can women reduce their breast density, and potentially their breast cancer risk, by taking medicines or by applying topical agents directly to the breast?

NCI’s Division of Cancer Prevention supports research on cancer screening and risk factors, including breast density, such as this clinical trial for women with dense breasts. NCIâs Division of Cancer Epidemiology and Genetics conducts research on risk factors for cancer, as explained in this article that explores the relationship between mammographic breast density and breast cancer.

Recommended Reading: How To Prevent Metastatic Breast Cancer

About Author: Lisa Coon

Lisa Coon is a Writing Coordinator for OSF HealthCare, where she has worked since August 2016. A Peoria native, she is a graduate of Bradley University with a degree in journalism. Previously, she worked as a reporter and editor at several newspapers in Iowa and Illinois.She lives in Groveland with her husband and son. In her free time she likes to cook, bake and read. She freely admits that reality TV is a weakness, and she lives by the quote, The beach is good for the soul.

Do I Still Need To Get Mammograms If I Have Dense Breast Tissue

New U Women

It is recommended that you still get regular mammograms even if you have dense breast tissue. It is important to discuss both your breast density and your risk factors for breast cancer with your healthcare provider when deciding when to start and how often to get regular mammograms. If you have dense tissue, your doctor may also suggest a tomosynthesis/3D exam, in addition to your usual mammogram to ensure that you are being thoroughly screened for breast cancer.

Last reviewed by a Cleveland Clinic medical professional on 08/07/2019.


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How Is Prevent Breast Cancer Helping

In addition to working with Breast Density Matters to raise awareness, Prevent Breast Cancers funded scientists are working hard to unlock the mysteries of this significant risk factor. Our current research projects on this topic include finding out what dense breast tissue is made of and which genetic changes occur within dense breasts that can lead to cancer developing.

The hope is that these projects could even lead to new preventative drugs in future that can lower breast density levels and therefore breast cancer risk. The charity would like to say a huge thanks to Tim Bacon Foundation for supporting our breast density research projects.

Cheryl Cruwys

In 2016, Cheryl Cruwys was diagnosed early with breast cancer she received minimal treatment and a positive health outcome due to supplemental screening on dense breast tissue . Voluntary roles include: Breast Density Matters UK and European Education Coordinator for

How Does Breast Density Affect Breast Cancer Risk

Are dense breasts a risk factor for breast cancer? Yes, women with dense breasts have a higher risk of breast cancer than women with fatty breasts, and the risk increases with increasing breast density. This increased risk is separate from the effect of dense breasts on the ability to read a mammogram.

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Annual Screenings Are Important

Allison Gleason, RT , an OSF HealthCare supervisor of mammography and ultrasound, said its important to remember that the density of a womans breasts can change over time. Thats why its important to get annual mammogram screenings to stay up-to-date on the condition of your breasts. Remember to continue to getting routine screening mammograms even when additional exams are suggested for you.

Breast tissue consists of fatty and fibroglandular tissue. Dense breast tissue is defined as having a higher percentage of fibroglandular tissue within your breasts. If more than 50% of your breasts is made of fibroglandular tissue, then your breasts are classified as dense.

The more fibrous and glandular tissue absorbs more radiation during mammography, reducing the accuracy of the test and making it more difficult to properly diagnose breast cancer. Dense breast tissue shows up white on a mammogram, as do tumors, which makes it more difficult to identify the difference.

According to the American Congress of Obstetricians and Gynecologists, a mammogram will identify 88% of cancers in a breast that is almost entirely fat, or low in density. Thats compared to 62% in high-density breasts.

How Is Breast Density Measured

Signs of high risk breast cancer – Mayo Clinic

When you have a mammogram, a radiologist reads the results using the Breast Imaging Reporting and Data System, or BI-RADS, published by the American College of Radiology. This is a standard system for reporting whats seen on the imaging.

BI-RADS uses an assessment scale from 1 through 6 to indicate whether there were no unusual findings or, if something was found, whether it was more likely benign or malignant . The report will also give a recommendation for routine screening or indicate what follow-up tests may be needed. An assessment of 0 means that additional imaging is first needed in order to characterize a potential finding.

In the BI-RADS report, the radiologist also includes a score for breast density on a scale from A through D:

A) Mostly fatty: The breasts are made up of mostly fatty tissue and contain very little fibrous and glandular tissue. About 10% of women have fatty breasts.

B) Scattered fibroglandular densities: The breasts are mostly fatty tissue, but there are a few areas of fibrous and glandular tissue visible on the mammogram. About 40% of women have scattered density.

C) Heterogeneously dense: A mammogram shows many areas of fibrous and glandular tissue. About 40% of women get this result.

D) Extremely dense: The breasts have large amounts of fibrous and glandular tissue. About 10% of women fall into this category.

A: Mostly fatty

Image copyright: and Dr. Wendie Berg

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Should Women With Dense Breasts Have Additional Screening For Breast Cancer

In some states, mammography providers are required to inform women who have a mammogram about breast density in general or about whether they have dense breasts. Many states now require that women with dense breasts be covered by insurance for supplemental imaging tests. A United States map showing information about specific state legislation is available from

Nevertheless, the value of supplemental, or additional, screening tests such as ultrasound or MRI for women with dense breasts is not yet clear, according to the Final Recommendation Statement on Breast Cancer Screening by the United States Preventive Services Task Force. Ongoing clinical trials are evaluating the role of supplemental imaging tests in women with dense breasts. NCIâs Cancer Information Service can tell you about clinical trials and provide tailored clinical trial searches to help you learn more about clinical trials related to breast density and breast cancer screening.

Recent research has suggested that for women with dense breasts, a screening strategy that also takes into account a womanâs risk factors and protective factors may be the best predictor of whether a woman will develop breast cancer after a normal mammogram and before her next scheduled mammogram.

As you talk with your doctor about your personal risk for breast cancer, keep in mind that:

Tips To Help If You Have Dense Breasts

  • Find out what screening options are best for you.Talk to your GP or breast surgeon about what is best for you.
  • Speak to your GP about how you can reduce any lifestyle risk factors. Although you cant change your breast density, there are a number of lifestyle changes you can make to reduce your risk of developing breast cancer and improve your overall wellbeing. These include maintaining a healthy weight, exercising regularly, reducing your alcohol intake and giving up smoking. Although these changes dont guarantee you wont develop breast cancer, theyll give you a start towards reducing your risk. You can learn more about risk factors for developing early breast cancer in My Journey.
  • Get to know your breasts and what is normal for you. Look in the mirror at your breasts and check your breasts from time to time. If you notice any changes such as a lump, nipple discharge or persistent new breast pain, please see your GP promptly – even if your last screening mammogram was normal.

More information

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How Do I Know If I Have Dense Breasts

Radiologists are doctors who read mammograms . They check your mammogram for abnormal areas, and they also look at breast density.

There are 4 categories of breast density. They go from almost all fatty tissue to extremely dense tissue with very little fat. The radiologist decides which of the 4 categories best describes how dense your breasts are:

Category A: Breasts are almost all fatty tissue.

Category B: There are scattered areas of dense glandular and fibrous tissue .

Category C: More of the breast is made of dense glandular and fibrous tissue . This can make it hard to see small masses in or around the dense tissue, which also appear as white areas.

Category D: Breasts are extremely dense, which makes it harder to see masses or other findings that may appear as white areas on the mammogram.

Mammogram reports sent to women often mention breast density. Your health care provider can also tell you if your mammogram shows that you have dense breasts.

In many states, women whose mammograms show heterogeneously dense or extremely dense breasts must be told that they have dense breasts in the summary of the mammogram report that is sent to patients .

The language used is mandated by each law, and may say something like this:

How Is Mammographic Density Classified

Breast Density

The level of mammographic density can be scored by radiologists along a scale from very low density to mostly dense . One of the most used scales is the American College of Radiologys Breast Imaging Reporting and Data System , which radiologists use to classify mammographic density as A, B, C or D. Sometimes a numerical scale of 1, 2, 3 or 4 is used.

  • Type A : around 10% of women have mostly fatty, very low-density breasts.
  • Type B : roughly 40% of women have this low level of density.
  • Type C : another 40% of women have this type of mammographic density, which is considered dense and may obscure small cancers.
  • Type D : around 10% of women have extremely dense breasts, which lowers the sensitivity of mammography.

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Should You Worry About Dense Breast Tissue

Breasts come in different shapes, sizes and densities.

In some cases, dense breast tissue can be associated with an increased risk of breast cancer.

A 2017 U.S. study revealed that four in 10 cases of breast cancer in younger women can be blamed on high breast density. The results show that breast density is a much more important breast cancer risk factor to be aware of than a persons family history. But having dense breasts is not an abnormal condition. In the United States, 43% of women over the age of 40 have dense breast tissue. Its basically a physical attribute of the body and theres little anyone can do to actively change or improve the density of their breast.

True Or False Dense Breast Tissue Means Your Breasts Are Heavy


Density refers to the appearance of your breast tissue on a mammogram not the actual weight of your breasts. Your breasts contain milk glands, milk ducts and connective tissue those are all dense breast tissue. The rest of the breast is made up of fatty tissue, which is the non-dense part. So, if you have dense breasts, you have more glands, ducts and connective tissue than fat.

Dense breast tissue appears white on a mammogram. Non-dense tissue appears transparent .

Cancer also appears white on a mammogram. Dense breast tissue is difficult to see through and could hide or mask cancerous growths.

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Who Reads My Mammogram To Determine If I Have Dense Breasts

After your mammogram, you will receive a written report with the radiologists findings. Radiologists are medical doctors who have completed a four-year residency in radiology and who specialize in diagnosing and treating conditions using medical imaging.

Breasts imaging specialists are radiologists who only read breast imaging exams. Early-stage cancers are more often detected by women who have their mammograms read by breast imaging specialists.

If your state doesnt require breast density to be included on a mammogram report, you can ask your radiologist to tell you your classification. With this information and your family history, your doctor can determine if you need more screening exams.

Why Is Breast Density Important

Dense breast tissue raises cancer risk

Breast density is important for two main reasons:

  • Women who have dense breast tissue have a higher risk of breast cancer compared to women with less dense breast tissue. Its unclear at this time why dense breast tissue is linked to breast cancer risk. It may be that dense breast tissue has more cells that can develop into abnormal cells.
  • Dense breast tissue also makes it harder for radiologists to see cancer on mammograms. Dense breast tissue looks white on a mammogram. Breast masses and cancers can also look white, so the dense tissue can make it harder to see them. In contrast, fatty tissue looks almost black on a mammogram, so its easier to see a tumor that looks white if most of the breast is fat tissue.

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Are There Different Categories Of Dense Tissue

Breast density is divided into four categories, ranging from having very little dense tissue to extremely dense tissue. The four categories are:

  • Type 1: Majority fatty tissue
  • Type 2: Some scattered dense tissue
  • Type 3: More dense tissue than fatty tissue
  • Type 4: Extremely dense tissue with very little fatty tissue

Most women are either type 2 or 3. This means they have some combination of dense and fatty tissue.

What Factors Influence Mammographic Density

There are some factors that can influence density levels to some extent, for example young women and women with a lower body mass index tend to have higher mammographic density.

Genetic factors are also important in determining the level of mammographic density. It is heritable, so women in the same family are likely to have the same density.

Other factors that can increase or decrease mammographic density to some extent include:

  • having children
  • being on hormone replacement therapy
  • going through menopause
  • being on tamoxifen .

All of these factors can change hormone levels in the body and influence mammographic density. However, while mammographic density usually declines with age, environmental influences or hormone levels, density is mostly determined when the breasts first form. This means some women will always sit in a high-density category compared with others in their age group, while others will always have lower density.

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What Is Breast Density

Breast density reflects the amount of fibrous and glandular tissue in a womans breasts compared with the amount of fatty tissue in the breasts, as seen on a mammogram.

On a mammography report, breast density is assigned to one of the following four categories

  • The breasts are almost entirely fatty .
  • A few areas of dense tissue are scattered through the breasts .
  • The breasts are evenly dense throughout .
  • The breasts are extremely dense .

Women in the first two categories are said to have low-density, non-dense, or fatty breasts. Women in the second two categories are said to have high-density or dense breasts. About half of women who are 40 years old or older have dense breasts.

How Do I Mitigate My Risk Of Breast Cancer

Breast density biggest risk factor of breast cancer

The survival rates for breast cancer have been improving since the 1980s, thanks to earlier detection from regular mammogram screening and improvements in breast cancer treatments. When breast cancer is found at an early stage, its more easily treated and the survival rate is much higher.

The best way to detect breast cancer early is by having regular screening mammograms before you develop symptoms of breast cancer like lumps, changes to the breast, or even pain in certain instances. This is why educating women about early detection is often the main goal of breast awareness month and its associated fundraisers and campaigns.

Having regular mammograms makes it easier for a radiologist to compare your images and see changes or areas of concern over time. If you wait until you have symptoms, the breast cancer might be enlarged and more difficult to treat.

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