What Are Factors That May Affect Breast Density?
1. Can I lower my breast density?
There are no guidelines or suggestions on how women can lower breast density, but some medications have been shown to help:
- For women who have had estrogen receptor-positive (ER-positive) breast cancer, a drug called tamoxifen or, after menopause, drugs called aromatase inhibitors (AIs) may be suggested to lower the chance of cancer returning.
- For women who have never had breast cancer but have had an “atypical biopsy” or are at higher risk for breast cancer, tamoxifen may be suggested to lower the chance of cancer growing. For women who cannot tolerate tamoxifen, raloxifene may be suggested to lower the chance of getting breast cancer.
- These drugs lower the chance that cancer will grow or return by blocking estrogen (a hormone that can stimulate the growth of some cancers). Blocking estrogen can also lower breast density. Tamoxifen and AIs have been shown to lower breast density but raloxifene has not. Not all women taking these drugs will experience lower breast density.
Talk to your healthcare professional to decide what is right for you.
2. Can I change my breast density with diet or exercise? Is my breast density related to the fat in my diet?
Fat content in what you eat and exercise do not directly change breast density. But if you lose or gain a lot of weight, your breasts can look more or less dense on your mammogram – though the amount of dense tissue will stay the same. This is because if you gain weight, there will be more fatty tissue (non-dense) in your breasts. If you lose weight, you will lose fatty tissue from your breasts. So, although the foods you eat and exercising do not change your breast density, your overall body fat can affect your breast density.
While exercise does not decrease the actual amount of dense tissue in your breasts, regular physical activity does decrease the overall risk of developing breast cancer.
For more information, see Q+A, “Will my breasts always be dense?”
3. Does taking estrogen affect breast density?
Yes. An increase in breast density is often seen in patients taking combined estrogen and progesterone hormone supplements (also called hormone replacement therapy, or HRT). This includes women and transgender patients using oral low-dose estrogen, vaginal estrogen, or transdermal estrogen treatment.
The increase in breast density often begins within a few months of starting hormone supplements. Hormones stimulate the growth of both normal and abnormal breast tissue. An increase in normal breast tissue increases breast density. Cancers that have estrogen receptors will also develop or grow as a result of hormone supplements. If you stop taking hormone supplements, your breast density and cancer risk decrease within months.
4. If I am a breast cancer survivor, does having dense breasts increase the chance of getting cancer in my opposite breast?
Yes. If you have dense breasts and have had breast cancer, there is a greater chance of developing cancer in the opposite breast (known as contralateral breast cancer). The good news is that this risk can be reduced with medications.
1. Raghavendra A, Sinha AK, Le-Petross HT, et al. Mammographic breast density is associated with the development of contralateral breast cancer. Cancer 2017; 123:1935-1940
2. Sandberg ME, Li J, Hall P, et al. Change of mammographic density predicts the risk of contralateral breast cancer–a case-control study. Breast Cancer Res 2013; 15:R57
3. Engmann NJ, Scott CG, Jensen MR, et al. Longitudinal changes in volumetric breast density with Tamoxifen and aromatase inhibitors. Cancer Epidemiol Biomarkers Prev 2017; 26:930-937
4. Cuzick J, Warwick J, Pinney E, et al. Tamoxifen-induced reduction in mammographic density and breast cancer risk reduction: a nested case-control study. J Natl Cancer Inst 2011; 103:744-752
5. Are lumpy or fibrocystic breasts the same thing as dense breasts?
No. Having “lumpy” or fibrocystic breasts is different than having dense breasts, but some women have both.
Normal breast tissue can feel lumpy whether it is fatty or dense. Cysts are common and noncancerous and sometimes are large enough to be noticed as a lump. Having dense breasts has nothing to do with the way your breasts look or feel. The doctor who reviews your mammogram determines whether you have dense breasts after looking closely at images from your mammogram.
6. Do men have dense breasts?
No. Normal male breasts do not contain dense tissue.
Sometimes men’s breasts do grow and look more like female breasts (known as gynecomastia). This can happen as men age or can be caused by some medicines.
It is important to remember that men can also get breast cancer. A mammogram can be done in men to check a lump.
7. Is breast density inherited?
8. Do Black women have denser breasts? Do Asian women have denser breasts? Do Hispanic women have denser breasts?
Many studies have found that Asian women more often have dense breasts than women of other races. Studies differ on whether Black or Hispanic women have denser breasts than non-Hispanic white women.
What matters most is your individual breast density. If you have dense breasts, you are more likely to get breast cancer and it is more likely to be missed on the mammogram.
9. What if I have dense breasts and a disease-causing BRCA gene variant (mutation)?
Disease-causing BRCA gene variants and dense breasts both increase the chances that a woman will get breast cancer. However, BRCA1 or BRCA2 variants put women at a much higher risk for getting breast cancer than the risk from having dense breasts.
Because BRCA gene carriers are more likely to get breast cancer at a younger age, they usually get a breast Magnetic Resonance Imaging (MRI) as part of their breast screening. In these women, breast screening should also start earlier, with MRI beginning at age 25 and mammography starting at age 30 or later.
MRI screening for women with BRCA variants is suggested whether or not they have dense breasts.