Dense breasts make the detection of small breast cancers on mammography a challenge. Breast tissue is white on a mammogram and fatty tissue is black on a mammogram. The density of a mammogram is based on the amount of black vs. white tissue and is described as fatty replaced, having scattered fibroglandular densities, heterogeneously dense, or extremely dense.
The white of dense breasts on mammography can obscure a small breast cancer, which can be hidden from the radiologist. As a screening tool, then, mammograms may not be the best study to search for a breast cancer in mammographic dense breasts.
So, what should a woman with dense breasts do for her yearly mammogram?
First, get your annual mammogram and read your mammogram report. The radiologist should describe the density of your breasts using one of the following phrases:
(1) fatty replaced
(2) scattered areas of fibroglandular density
(3) heterogeneously dense
(4) extremely dense
A heterogeneously dense (3) or extremely dense (4) mammogram is considered dense. If your mammogram is read as dense, then further studies may be necessary. Breast MRI, Breast Ultrasound or Digital Breast Tomosynthesis (DBT), known as both 3D-Mammography and 3D-Tomography may be recommended.
Breast MRI is the best study, but is also the most expensive and may not be covered by insurance. Breast Ultrasound (US) is much less expensive and is a very good alternative to MRI. 3D-Mammography (DBT) is the least expensive study but carries the risk of increased radiation exposure, which will be the equivalent of 3-4 weeks of normal background radiation that we all receive just by living.
For now, each choice must be individualized for women with dense breasts, i.e. category (3) or (4) above. If you are at high risk for breast cancer, perhaps you should have a Breast MRI. If you are at moderate risk, perhaps you should have a Breast Ultrasound. If you are at average to low risk, maybe a 3D-Mammogram is sufficient.
For the average American woman, who does not have a known genetic mutation and who has not had breast cancer, five-year and lifetime risk of developing breast cancer is calculated using the NCI Breast Cancer Risk Assessment Tool based on the Gail Model. The five-year risk is considered average if below 1.7% and high if above 1.7%. The lifetime risk, as a general guideline, is average if below 14%; moderate if 14%-20%; and high if greater than 20%.
There are no good studies of additional imaging in women with dense breasts. You need to talk with your physician and weigh the benefits of additional imaging based on your risk assessment against the risks of additional imaging. The risks can be cost, stress, additional radiation exposure, unnecessary biopsy of a suspicious lesion that proves to not be cancer and complications of those procedures.
Keep in mind that your health insurance may not pay for additional imaging studies. If cost is a concern, 3D-Mammography (DBT) is the least expensive option, although there is an increased exposure to radiation.
A clinical trial, TMIST, is trying to determine if there is a benefit for 3D-Mammogram (DBT) in addition to 2D-Mammogram for the average woman. The trial does not consider the density of the breast.
And lastly, these recommendations are for screening. If you have a breast lump, nipple discharge or other breast symptom, then you need to see your physician or provider and have a diagnostic breast imaging evaluation.
Get your mammogram every year. If you have a breast lump, see your doctor.