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Patient Questions and Answers

WHAT IS BREAST DENSITY AND WHY DOES IT MATTER?

1. What is breast density, does it have something to do with the look/feel of my breasts? X

All breasts contain glands, fibrous tissue, and fat. Dense tissue is made of glands and fibrous tissue (referred to as "fibroglandular" tissue). Dense tissue blocks x-rays and therefore shows up white on a mammogram. Fatty tissue allows more x-rays to penetrate and therefore shows up as black or dark gray on a mammogram. Each woman's breasts are different than the next and contain a unique mix of fatty and dense tissue. Some women's breasts are almost all fat, some have very little fat, and some are in between. Dense breasts are normal and become less so with age and menopause. Breast density is not determined by how a breast looks or feels. The radiologist can determine the breast density by examining the images from a mammogram.

Figure A. Courtesy of Jeremy M. Berg. Ph. D. Figure B.

Diagrams of the normal breast. A) The normal breast is composed of milk-producing glands at the ends of ducts leading to the nipple. There is layer of fat just beneath the skin. Often a few lymph nodes are seen near the underarm (axilla). B) On a mammogram, fat appears dark gray, and glandular tissue, fibrous tissue, muscle, and lymph nodes appear light gray or white. Masses due to cancer also appear white.

2. Women often ask "How To Diagnose Dense Breast Tissue?" How is breast density on a mammogram determined?X

A radiologist evaluates the density of a breast as part of reading a mammogram. The density is categorized (see below) and is usually in the report sent from the radiologist to the referring doctor.

A woman's breast tissue is described on mammography as one of four categories:


Mammographic images representative of the four categories of breast density:
(A) Fatty; (B) Scattered fibroglandular tissue; (C) Heterogeneously dense; (D) Extremely dense
Breasts which are (C) heterogeneously dense, or (D) extremely dense, are considered "dense breasts"

A. ALMOST ENTIRELY FATTY – On a mammogram, most of the tissue appears dark gray or black while small amounts of dense (or fibroglandular) tissue display as light grey or white.
About 10% of all women have breasts considered to be "fatty."

B. SCATTERED FIBROGLANDULAR DENSITY – There are scattered areas of dense (fibroglandular) tissue mixed with fat. Even in breasts with scattered areas of breast tissue, cancers can sometimes be missed when they look like areas of normal tissue or are within an area of denser tissue.
About 40% of all women have breasts with scattered fibroglandular tissue.

C. HETEROGENEOUSLY DENSE – There are large portions of the breast where dense (fibroglandular) tissue could hide masses.
About 40% of all women have heterogeneously dense breasts.

D. EXTREMELY DENSE – Most of the breast appears to consist of dense (fibroglandular) tissue creating a "white out" situation, making it extremely difficult to see through.
About 10% of all women have extremely dense breasts.

3. How do I know the answer to the question: Are you dense? X

Breast density information may be provided by a health care professional or may also be included in the letter you receive after your mammogram. Many states now have laws that require breast density information to be included in the letter you receive with your mammogram results. Even if you do not live in a state with a breast density inform law, you can ask your health care provider for this information as it is routinely included in the description of findings in the mammogram report. Click HERE to see what the breast density reporting requirement is in your state.

4. Why does breast density matter on my mammogram?X

On a mammogram, cancer is white. Normal dense tissue also appears white. If a cancer develops in an area of normal dense tissue, it is harder or impossible to see it on the mammogram, like trying to see a snowman in a blizzard. If a cancer (white) develops in an area of fat (black), it usually can be seen easily, even when it is small. Because dense tissue can hide cancers, as density increases the ability of mammography to show cancers decreases.
The images below are examples of how cancer looks in each of the breast density categories.


Courtesy of Dr. Regina Hooley

A) A small cancer (arrow) is easily seen in a fatty breast. B) In this breast categorized as having "scattered fibroglandular" density, a large cancer is easily seen (arrow) in the relatively fatty portion of the breast, though a small cancer could have been hidden in areas with normal glandular tissue. C) In this breast categorized as "heterogeneously dense," a 4 cm (about 1.5 inch) cancer (arrows) is hidden by the dense breast tissue. This cancer has also spread to a lymph node under the arm (curved arrow). D) In this extremely dense breast, a cancer is seen because part of it is located in the back of the breast where there is a small amount of dark fat making it easier to see (arrow and triangle marker indicating lump). If this cancer had been located near the nipple and completely surrounded by white (dense) tissue, it probably would not have been seen on mammography.

5. Do dense breasts affect my risk of getting breast cancer?X

Yes. In addition to obscuring cancers on mammography, dense breast tissue can increase your risk of getting breast cancer. The risk increases with increasing breast density. Women with the densest breasts have a risk for breast cancer that is 4- to 6-times higher than that of women with the least dense breasts.* The majority of women will fall in between these extremes.

There are probably several reasons that dense tissue increases risk. One is that the glands tend to be made up of relatively actively dividing cells which can mutate and become cancerous: the more glandular tissue, the greater the risk. The second is that the local environment around the glands may produce certain growth hormones that stimulate cells to divide, and this seems to be more true for fibrous tissue than for fatty tissue. Supplemental screening in addition to mammography should be considered for women with dense breasts.

Of course, risk for developing breast cancer is influenced by a combination of factors including age, family history of cancer (particularly breast and/or ovarian cancer), and prior atypical breast biopsies (where breast cells have begun to change shape but are not cancerous – usually will be monitored). However, the largest study** of its kind found that dense breast tissue increases the risk of developing breast cancer more than family history, postmenopausal weight gain, or late childbearing.

Print and discuss the Risk Checklist English | Spanish with your health care provider

*American Cancer Society. Breast Cancer Facts & Figures 2013-2014. Atlanta: American Cancer Society, Inc. 2013. Retrieved from: http://www.cancer.org/acs/groups/content/@research/documents/document/acspc-042725.pdf

**Engmann NJ, Golmakani MK, Miglioretti DL, Sprague BL, Kerlikowske K, for the Breast Cancer Surveillance Consortium. Population-Attributable Risk Proportion of Clinical Risk Factors for Breast Cancer. JAMA Oncol.Published online February 02, 2017. doi:10.1001/jamaoncol.2016.6326

WHAT SHOULD I KNOW ABOUT DENSE BREASTS?

6. Is it unusual to have dense breasts?X

No. Dense breasts are neither unusual nor abnormal. By age:

  • More than half of women under the age of 50 have dense breasts
  • About 40 percent of women in their 50s have dense breasts
  • About 25 percent of women aged 60 and older have dense breasts

During pregnancy and breastfeeding, the dense tissue grows and the breasts become denser and often larger. With menopause the breast is no longer periodically stimulated with hormones (unless you take hormone supplements) and glandular tissue (which contributes to breast density) tends to decrease since you no longer need to breastfeed.

Your breasts are unique and can change over time, which is why women should know their own breast density and understand the limitations of mammography for their breast type.

7. Is breast size related to breast density?X

Smaller breasts tend to be dense, and large breasts are more often relatively fatty, but there is wide variation at the individual level.

8. I have been told my breasts are "dense." How do I find out which density category they are?X

Information about your specific density category (heterogeneously dense or extremely dense) is usually included in the report that is sent from the radiologist who performed your mammogram to your health care provider. You can contact either for the information.

9. Will my breasts always be dense?X

Breasts tend to become less dense as you get older (see Figure below), especially after menopause as the glandular tissue (which produces milk) can shrink and the breast may appear more fatty. If you lose a lot of weight, your breasts may appear denser due to the relative loss of fat. The visual assessment of breast density is somewhat subjective and the radiologist may describe your density as scattered one year and heterogeneously dense the next year even if there has not been a true change in your breast density.

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Courtesy of Dr. Wendie Berg

10. Do I need to know my breast density before I begin getting mammograms?X

Dense breasts are mostly an issue related to the effectiveness of a mammogram so that you won't know your breast density until you start having mammograms. For women determined to be at normal risk by their health care provider, mammography is often recommended to begin at age 40. If you have a family history of breast cancer and have not begun mammography screening, speak to your health care provider about your personal risk factors and what screening plan is right for you.

11. If I don't have dense breasts, what should I do?X

Annual mammography is recommended if you are over the age of 40 and in good health. Tomosynthesis can be used in addition to mammography. If your health care provider determines you are at high risk of developing breast cancer, you may be recommended to have an MRI every year in addition to mammography.

WHAT DO I NEED TO KNOW ABOUT MAMMOGRAMS AND DENSE BREASTS?

12. Can my mammogram be "normal" if I have dense breasts?X

Yes. Dense breasts are “normal.” On average, about 40% of women of mammography age have dense breasts. However, because dense breast tissue can hide cancer on a mammogram it may reduce the ability of your radiologist to find cancer if present. A “normal,” “negative,” or “benign” mammogram does not reliably exclude cancer in women with dense breasts. Women with dense breasts may have cancer detected soon after a “normal” or “negative” mammogram (this is known as an “interval cancer”). If your mammogram shows you have dense breasts, you should discuss the possibility of additional screening with your health care provider.

13. If mammograms miss cancers in dense breasts, should I still have a mammogram?X

Yes. Having dense breasts makes the mammogram less accurate than in a woman with fatty breasts, but it does not make it worthless. To date, mammography is the only breast cancer imaging screening tool ever studied to determine if there is a relationship between finding cancers early and reducing death. Multiple studies have proven that early detection of cancers by mammography reduces the risk of death due to breast cancer for women aged 40 to 74 years. While additional screening may be recommended for women with dense breasts and/or high risk for developing breast cancer, there are still some cancers and precancerous changes that will show on a mammogram better than on ultrasound or MRI (Figure below). Wherever possible, women with dense breasts should have digital mammography rather than film mammography, due to slightly improved cancer detection using digital mammography.


Courtesy of Dr. Wendie Berg

Mammography Shows Some Early Breast Cancers not seen on Ultrasound. Magnification mammographic images of heterogeneously dense breasts show new grouped calcifications (white specks that are like salt crystals [within yellow circles]). These are difficult to see with ultrasound. Most calcifications seen on mammograms are not due to cancer; however, biopsy showed these to be due to ductal carcinoma in situ (DCIS), a noninvasive cancerous change which, if left untreated, can progress to invasive breast cancer.

14. What is a mammogram and are there different types?X

Mammograms are low-dose x-rays of the breast that have been used for screening since the 1980s. There are three different types of mammography:

  • Film, 2-Dimensional, known as "analog"
  • Digital, 2-Dimensional, known as "Full Field Digital Mammogram" (FFDM). Over 90% of mammography facilities in the U.S. offer digital mammograms.
  • Tomosynthesis, also referred to as "3-Dimensional" or "tomo," is a new technology which is becoming more widely available.

Digital mammograms perform a little better in dense breasts than do film mammograms. All types of mammograms use x-radiation to produce an image. X-rays have difficulty penetrating dense tissue and are more effective in fattier breasts than in extremely dense breasts. The radiation exposure from a mammogram is only to the breasts and results in an effective dose to the whole body which is less than 10% of the normal background radiation just from living on Earth for one year.

15. Are a digital mammogram and a 3D mammogram (known as tomosynthesis) the same thing?X

No, but they are different types of mammograms. Both involve computer generated images. A 2-D mammogram captures images from two different angles (or views). Tomosynthesis (3-D) captures images from many different angles. The multiple images are then compiled by a computer and used to create thin "slice" images of your breast. A "3D" mammogram is usually performed in addition to a standard 2D-mammogram. Tomosynthesis uses x-rays that produce about the same radiation exposure to the breasts as a standard mammogram: if you have both 2D and 3D, your breasts will receive nearly twice the amount of radiation as from a standard mammogram, though the combined dose is still within standard safety limits. In some facilities, a "synthetic" 2D mammogram can be created from the tomosynthesis images and can replace the standard 2D mammogram, in which case the radiation dose is the same as for a standard 2D mammogram.

A 2D mammogram finds about 2-7 cancers for every 1,000 women who have a mammogram. Another 1-2 cancers will be found per 1,000 women when tomosynthesis is added to a standard mammogram, and these results are seen across all breast densities. Though, a cancer "hidden" on a 2D mammogram could still be hidden on a 3D mammogram unless it is surrounded by fatty tissue. Tomosynthesis does makes it easier to identify normal tissue (vs. an area which might have needed more follow-up based on a 2D mammogram) and therefore reduces the chance of being called back for additional views or an ultrasound. In the near future, it is expected to be routine to have tomosynthesis as part of the routine screening, particularly if the facility has the ability to generate synthetic 2D mammograms.

2D and 3D mammogram cancer find (detection) rates

If 1,000 Women Are Screened With

Number of Women Found to Have Cancer

Type of Technology

Number of Women Called Back for More Testing

Regular 2D-mammogram alone

2-7 total

Ionizing Radiation

100

2D-mammogram plus 3D-mammogram
(tomosynthesis)

Mammogram 2-7 + Tomosynthesis 1-2
=3-9 total

Ionizing Radiation

70

Regular 2D-mammogram plus ultrasound (US) *

Mammogram 2-7 +
Ultrasound 2-4
=4-11 total

Sound waves

170-230

Regular 2D-mammogram plus contrast-enhanced MRI

Mammogram 2-7 +
MRI 10 or more
=12-17 or more total

Magnetic field and intravenous contrast

160-220

* One prospective multicenter trial in Italy (ASTOUND) examined ultrasound and 3D mammography after 2D mammography, reporting ultrasound identified 7 more cancers per 1000 women screened compared to 4 more cancers per 1000 women screened with 3D mammography.

16. Does it matter where I have my mammogram?X

Yes. To legally perform mammography, a facility must be certified and recognized by the U.S. Food and Drug Administration (FDA) who maintains a Mammography Facility Database. Accredited facilities must abide by strict standards for image quality – and it is from these images that your breast density will be determined. Click Here for the list of FDA recognized accredited facilities.

An imaging center may also receive further accreditation through the American College of Radiology (ACR). The ACR's accreditation program, which designates Diagnostic Imaging Centers of Excellence®, assesses imaging centers for a number of qualifications (e.g. personnel, policies, equipment, image quality and patient care) and such centers also must have ACR accreditation for stereotactic and ultrasound-guided breast biopsy. Click Here for a list of ACR Diagnostic Imaging Centers of Excellence.

I HAVE BEEN TOLD I HAVE DENSE BREASTS, WHAT SHOULD I DO?

17. What are other screening options after my mammogram?X

Depending on your age, your risk level (as determined by a health care provider), and your breast density, additional screening, like ultrasound or MRI may be recommended in addition to mammography. The addition of another imaging tool after your mammogram will find more cancers than mammography alone, though most women being screened do not have breast cancer.

It is important to understand that it is normal for any screening test to find things that may need to be looked at more closely by additional screening. While some of these additional findings may be cancerous, the vast majority will not (and this is known as a "false positive"); the only way to determine the importance of such findings is through additional imaging and sometimes biopsy. You need to consider your own tolerance for false positives compared to the potential benefit of improved cancer detection when deciding whether or not to have additional screening.

Ultrasound: Ultrasound is the only screening procedure suggested specifically for women with dense breasts. In dense tissue, ultrasound has been shown to find another 2-4 cancers per 1000 women screened that were not seen on mammography or tomosynthesis. Like all screening tools, ultrasound also detects many findings that are not cancer (false positives), but which may require follow-up imaging and/or biopsy. There is no x-ray radiation from ultrasound.

MRI: Contrast-enhanced magnetic resonance imaging (MRI) can find the most breast cancers of any imaging procedure currently in widespread use. MRI of the breasts requires intravenous injection of contrast and lying in a tunnel. If you are at very high risk for breast cancer (due to a known or suspected mutation in a breast cancer causing gene, or due to a greater than 20% lifetime risk for breast cancer as determined by your health care provider), you may be eligible to begin screening at age 25 or at least by age 30. In high-risk women, MRI is recommended annually in addition to mammography regardless of breast density, though before age 30 sometimes only MRI is performed due to the radiation sensitivity of younger breast tissue. Annual screening MRI is also recommended in women who have had prior radiation therapy to the chest at least 8 years earlier and before age 30, such as for Hodgkin lymphoma.

MRI's have many false positives (when an exam result indicates cancer may be present when it is not). The benefits and risks of MRI in women who are not at high risk are being studied. In most centers, MRI is a very expensive imaging tool that is often not covered by insurance unless a woman meets high-risk definitions. MRI cannot be performed in women with poor kidney function, pacemakers, or certain other metal implants. There is no x-ray radiation from MRI.

The addition of screening ultrasound is usually only recommended in women with dense breasts. Screening contrast-enhanced MRI is used in high-risk women of all breast densities. If you have screening with Contrast-Enhanced MRI, you do not need screening ultrasound.

Cancer find rates when Ultrasound or MRI is added to mammography

If 1,000 Women Are Screened With

Number of Women Found to Have Cancer

Type of Technology

Number of Women Called Back for More Testing

Regular 2D-mammogram alone

2-7 total

Ionizing Radiation

100

2D-mammogram plus 3D-mammogram
(tomosynthesis)

Mammogram 2-7 + Tomosynthesis 1-2
=3-9 total

Ionizing Radiation

70

Regular 2D-mammogram plus ultrasound (US) *

Mammogram 2-7 +
Ultrasound 2-4
=4-11 total

Sound waves

170-230

Regular 2D-mammogram plus contrast-enhanced MRI

Mammogram 2-7 +
MRI 10 or more
=12-17 or more total

Magnetic field and intravenous contrast

160-220

Courtesy of Dr. Wendie Berg

* One prospective multicenter trial in Italy (ASTOUND) examined ultrasound and 3D mammography after 2D mammography, reporting ultrasound identified 7 more cancers per 1000 women screened compared to 4 more cancers per 1000 women screened with 3D mammography.

18. If I have a 3D mammogram (tomosynthesis), do I also need a screening ultrasound or MRI?X

If you have been recommended to have a MRI screening, yes, you would still have MRI even if you have tomosynthesis. Research studies on ultrasound after tomosynthesis are being performed, however a recent large trial* in Italy found that ultrasound significantly improved detection of cancer even after tomosynthesis (3D mammography) in women with dense breasts.

*(2016). Taglifico AS, Calabrese M. Mariscotti G, et al. Adjunct screening with tomosynthesis or ultrasound in mammography-negative dense breasts (ASTOUND): Interim report of a prospective comparative trail. J Clin Onco. Epub March 9, 2016

19. Should a routine annual mammogram for a woman with dense breasts be scheduled as a “diagnostic” or a “screening” mammogram?X

A. Screening. “Diagnostic” mammography is monitored by the radiologist during the appointment and “screening” mammography is not. Indications for diagnostic mammography, rather than screening, include signs and symptoms of breast cancer such as a lump, bloody or spontaneous clear nipple discharge, skin or nipple retraction. If additional targeted imaging or follow-up is needed for an abnormality seen on the most recent prior breast imaging, a “diagnostic” appointment is also appropriate. In diagnostic breast imaging, additional views or ultrasound may be performed at the same visit if they are needed. The radiologist will interpret the breast imaging during the examination and the woman will leave with her results after a diagnostic mammogram. Women with a personal history of breast cancer can have their routine annual mammograms performed as diagnostic or screening examinations at many facilities. Diagnostic mammography is typically covered by insurance but subject to deductible and copay.

“Screening” mammography is fully covered by insurance under the Affordable Care Act for women over the age of 40 in the United States and may be covered for younger women, if recommended by her physician, depending on the insurance policy. Typically, screening mammograms are interpreted in a quiet, uninterrupted environment with the full benefit of prior examinations. Cancers are better detected and fewer unnecessary additional views (with associated radiation exposure) are recommended in the screening setting. Results are usually sent by mail to the patient within a few days to a week (by law not later than 30 days) after the appointment.

20. If I am recommended to have additional screening with ultrasound or MRI, will I need to have that every year?X

Usually the answer is yes, but, as you age, your personal risks and the benefits and types of additional screening recommended may change. Together with your doctor, it is important to reassess your risks every year or two and determine what screening plan is best for you. Technology is changing and guidelines also evolve which influence recommendations.

21. Is MBI or BSGI recommended for screening dense breasts?X

Molecular Breast Imaging (MBI) and Breast Specific Gamma Imaging (BSGI) are specialized nuclear medicine procedures for the breast that can detect cancers hidden within dense tissue on a mammogram. These tests require an intravenous injection of a small amount of radioactive material, which circulates throughout the body. Breast cancers can be seen because the radioactive material is taken up by cancer cells more than normal cells. The ability of these tests to show cancer is not affected by the breast density. The radiation from these tests is to the whole body (unlike mammography which is a lower dose to just the breasts).

Although ongoing studies evaluating a low-dose version of MBI as a screening tool for dense breasts are showing excellent results, MBI and BSGI are most often used as diagnostic tools in dense breasts. A diagnostic tool is one which helps diagnose cancer once a symptom appears (like a lump that can be felt but which cannot be seen on mammography or ultrasound) or when there is a suspicious area on a mammogram that remains vague after additional mammographic views and ultrasound. MBI or BSGI can also be helpful for some women who need but cannot have an MRI. These tests are never used in women who are pregnant.

22. Should thermography be used for screening dense breasts?X

No. Thermography is a technique that uses infrared technology to detect both heat and blood flow patterns very near the skin's surface and some large cancers can be seen this way. However, thermography has a high "false negative" rate (when a test result indicates "no cancer" even though cancer is actually present), especially for small breast cancers. It can also have false positives (when a test result indicates cancer may be present when it is not). According to the FDA*, "Despite widely publicized claims to the contrary, thermography should not be used in place of mammography for breast cancer screening or diagnosis."

*(2011). Thermogram no substitute for mammogram. U.S. Food and Drug Administration. Retrieved from http://www.fda.gov/forconsumers/consumerupdates/ucm257499.htm

23. Will my insurance cover any additional screening?X

The answer depends on the type of screening, your insurance, risk factors, the state you live in, and whether or not a law is in effect requiring insurance coverage for additional screening. In Illinois, for example, if ordered by your health care provider, a woman with dense breasts can receive an ultrasound without a copay or deductible. In New York beginning January 1, 2017 all supplemental screening and diagnostic breast imaging are required to be fully covered (no copay/no deductible), though exceptions do exist. Connecticut, an ultrasound co-pay for screening dense breasts cannot exceed $20. Generally, in other states, an ultrasound will be covered if ordered by your physician - but is subject to the copay and deductible of your individual health plan. In New Jersey, insurance coverage is provided for additional testing if a woman has extremely dense breasts. An MRI will generally be covered if your health care provider has determined you meet "high-risk"* criteria but MRI is typically subject to the copay and deductible of your individual health plan. It is important to check with your insurance carrier prior to having additional screening. For information about insurance coverage within your state, visit the Legislation Tab’s interactive map for more details.

*For more information on high-risk criteria, see American Cancer Society guidelines: http://www.cancer.org/cancer/breastcancer/moreinformation/breastcancerearlydetection/breast-cancer-early-detection-acs-recs

WHAT ARE FACTORS THAT MAY AFFECT BREAST DENSITY?

24. Can I change my breast density with diet? Is the fat in my diet related to my breast density?X

Diet has little to do with breast density. However, it does relate to overall body fat which is factored into your body mass index (BMI). BMI is a measure of body fat based on height and weight. BMI and breast density are both separate and independent risk factors for breast cancer. Before menopause, low BMI increases the risk of breast cancer. After menopause, weight gain and increasing BMI increase the risk of breast cancer. Please speak to your doctor about the optimal BMI for your body type.

25. Does taking estrogen affect breast density? X

An increase in breast density is much more common among women taking combined (estrogen plus progesterone) hormonal therapy (HRT), than for those using oral low-dose estrogen or transdermal estrogen treatment. The increase in density is often apparent at the first visit after starting hormonal therapy. The risk of breast cancer also increases in women taking combined hormonal therapy.

26. Can I decrease my breast density by taking tamoxifen? X

In some women, tamoxifen does decrease breast density. Tamoxifen blocks the estrogen receptor in breast cells and in breast cancer cells which express the estrogen receptor. Tamoxifen may be recommended to reduce the risk of developing breast cancer in women who have had prior atypical biopsies or who are otherwise at elevated risk for breast cancer. Tamoxifen is also prescribed to decrease the likelihood of recurrence in women who have had breast cancer that expresses estrogen receptors. Early studies suggest that only women who experience a decrease in their breast density while taking tamoxifen can benefit from decreased risk of subsequent (estrogen-receptor positive) cancer. The change in breast density due to tamoxifen is small and usually requires computer measurement to be recognized. Tamoxifen also carries risks of blood clots and cancer of the lining of the uterus.

27. Will taking Arimidex or other aromatase inhibitors affect my breast density?X

Aromatase inhibitors block the body's own production of estrogen and are prescribed for postmenopausal women who have had breast cancer classified as "estrogen positive." One study* looked at women who have had breast cancer. When breast density is carefully measured by computer software, women who experienced a decrease in breast density while taking aromatase inhibitors had a lower risk of recurrence than women who did not experience a decrease in breast density.

* Kim, J, Han, W, Moon, H, et al. (2012). Breast density change as a predictive surrogate for response to adjuvant endocrine therapy in hormone receptor positive breast cancer. Breast Cancer Research 2012 14(403). Retrieved from
http://breast-cancer-research.com/content/14/4/R102

Kim, J, Han, W, Moon, H, et al. (2012). Correction: Breast density change as a predictive surrogate for response to adjuvant endocrine therapy in hormone receptor positive breast cancer. Breast Cancer Research 2012 14(403). Retrieved from
http://breast-cancer-research.com/content/14/6/403

28. If I am a breast cancer survivor and reduce my breast density with medication, does this reduce my risk of developing cancer in the other breast?X

A recent study* indicates so. The study showed that breast cancer survivors taking tamoxifen or an aromatase inhibitor who experienced at least a 10% decrease in breast density within the first two years after their original diagnosis, had a significantly lower risk of cancer in the opposite breast (known as contralateral breast cancer). This potential new risk predictor can thus contribute to decision-making in follow-up treatment - particularly the continuation of a chemoprevention drug, like tamoxifen or aromatase inhibitors, which reduce breast density in some women.

* Sandberg, M, Li, J, Hall, P, et al. (2013). Change of mammographic density predicts the risk of contralateral breast cancer – a case control study. Breast Cancer Research (15). Retrieved from http://breast-cancer-research.com/content/15/4/R57

29. Do lumpy breasts or fibrocystic breasts mean I have dense breasts?X

Having "lumpy" breasts doesn't mean you have dense breasts. Fatty breasts can feel lumpy as the ligaments which support the breast can surround fat lobules and make them feel almost like soft grapes.

A fibrocystic breast is not the same as a dense breast. Fibrocystic change is a benign (non-cancerous) hormonal condition that is most pronounced when women are young and usually decreases after menopause. Fibrocystic breasts can appear dense due to cysts and/or areas of fibrosis (which resemble scar tissue). Cysts are small sacs of fluid in the ends of ducts where milk could have been produced. Cysts are very common and do not increase your risk for breast cancer; however, some other fibrocystic changes indicate active areas (known as "proliferative changes") in the breast which do slightly increase your risk for breast cancer.

30. Is breast density an issue that affects men?X

Not normally, though men do get breast cancer. Normal male breasts are mostly fatty. Sometimes men's breasts do become enlarged and develop glandular tissue due to a condition called gynecomastia. This enlargement, due to a hormonal imbalance, normally affects one breast more than the other. If a mammogram is performed, it is usually easy to distinguish from breast cancer.

31. Does exercise affect my breast density?X

No. Exercise can increase the amount of muscle behind your breasts, but the actual breast tissue is not affected by exercise. If you lose a lot of weight while exercising - the breasts can appear denser due to loss of fat (because the quantity of fat decreases while the quantity of dense tissue stays the same).

32. Can breast density be inherited?X

Breast density is at least partially inherited, though it is complex to predict. If your mother has dense breast tissue, it's more likely you will, too.

33. Does the increase in breast density while I am breastfeeding affect the accuracy of my mammogram?X

Yes. Changes in the breast during breastfeeding do reduce the accuracy of screening tests (like mammography or MRI). Unless you plan to be breastfeeding for more than one to two years and are at high risk, it is generally recommended to wait at least a few months after you stop breastfeeding before resuming breast screening. Ultrasound is usually performed first if you have concerning breast symptoms while breastfeeding.

34. Do African-American women have denser breasts?X

There have been conflicting studies on whether African-American women have denser breasts than women of other races. One study* indicated they do not, while a more recent study** indicated they do.

*Reference: Del Carmen, MG, Halpern, EF, Kopans, DB, et al. (2007). Mammographic breast density and race. American Journal of Roentgenology 138(4): 1447-1150. Retrieved from http://www.ncbi.nlm.nih.gov/m/pubmed/17377060/

**McCarthy AM, Keller B, Synnestvedt M, Conant E, Armstrong K, Kontos D. Racial differences in quantitative measures of area and volumetric breast density [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; 2015. Abstract nr 2770

35. Do Asian women have denser breasts?X

Generally, Asian women do have denser breasts than women of other races.

36. What if I have dense breasts and a disease-causing BRCA gene mutation?X

BRCA gene mutations that cause disease and dense breasts are each independent risk factors for the development of breast cancer. However, BRCA1 or BRCA2 mutations are associated with a much higher risk than that of having dense breasts. As BRCA1 and BRCA2 mutations are associated with a higher risk, MRI is part of routine screening after the age of 25 in women known to have these mutations, regardless of breast density. Cancers are also more likely to develop at a younger age in women with disease-causing mutations in BRCA genes, and the breasts are usually dense at younger ages making mammography especially ineffective as a standalone test in such women.