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August 27, 2010 | Comments: 1

Breast Density: An Emerging Risk Factor for Cancer

Dense breasts make it harder to read a mammogram. Now it’s thought that having dense breasts is a risk factor itself for breast cancer.

Only a mammogram can determine if you have dense breasts. Size, shape, and weight—either of the breast or the person—offer no clue. The tissue in the breast consists of fat cells and glandular cells, as well as connective tissue and other specialized structures. The fewer fat cells in the breast, the denser the tissue. Dense breast tissue looks white on a mammogram and is more difficult to evaluate—not as much can be seen, whereas fat cells provide clearer contrasts. This is one reason women with dense breasts may have tumors that go undetected—making the prognosis worse.

A Canadian study in the New England Journal of Medicine a few years ago found that women with dense breasts had a higher risk of developing breast cancer. Risk rose with the proportion of dense tissue in the breast. Evidence so far suggests that especially dense breasts may reflect increased breast tissue growth—growth that may predispose to developing cancer.

If you want to know whether your breast tissue is dense, ask your radiologist or physician the next time you have a mammogram. Those most likely to have dense breasts are younger women, those who have never been pregnant, women who had children when older, or those who have been on hormone therapy. Increasing age after menopause tends to decrease density.

What to do

If you do have dense breasts, you and your doctor should discuss whether you need other kinds of tests in addition to mammograms and an annual clinical breast exam. They may be warranted, especially if you have a strong family history (close relatives with breast cancer, particularly before menopause), have already had a biopsy or breast cancer, or have some other combination of risk factors.

Ultrasound imaging (also called sonography) and MRIs (magnetic resonance imaging) are widely used as adjuncts to mammography, though there’s no standard recommendation about this. The American Cancer Society recommends MRI screening only for women deemed to be at very high risk because of genetic and/or other significant risk factors. MRIs can be useful after a suspicious finding on a mammogram, but they can produce false-positives, requiring still further and more invasive testing. Another drawback—insurance may not cover the tests. 

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