What is the role of mammography in breast cancer screening?

Updated: Apr 10, 2019
  • Author: Erin V Newton, MD; Chief Editor: Marie Catherine Lee, MD, FACS  more...
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Mammography is a special type of low-dose x-ray imaging used to create detailed images of the breast. Mammography is currently the best available population-based method to detect breast cancer at an early stage, when treatment is most effective. Mammography can demonstrate microcalcifications smaller than 100 µm; it often reveals lesions before they become palpable by clinical breast examination (CBE) and, on average, 1-2 years before being found by breast self-examination (BSE). An estimated 48 million mammograms are performed each year in the United States.

The US Preventive Services Task Force (USPSTF) estimates the benefit of mammography in women aged 50-74 years to be a 30% reduction in risk of death from breast cancer. For women aged 40-49 years, the risk of death is decreased by 17%.

There are 2 types of mammography examinations: screening and diagnostic. Screening mammography is done in asymptomatic women. Diagnostic mammography is performed in symptomatic women (eg, when a breast lump or nipple discharge is found during self-examination or an abnormality is found during screening mammography). This examination is more involved, time-consuming, and expensive than screening mammography and is used to determine the exact size and location of breast abnormalities and to image the surrounding tissue and lymph nodes. Women with breast implants or a personal history of breast cancer will usually require the additional views used in diagnostic mammography.

The American College of Radiology (ACR) has established the Breast Imaging Reporting and Data System (BI-RADS) to guide the breast cancer diagnostic routine. BI-RADS is the product of a collaborative effort between members of various committees of the ACR in cooperation with the National Cancer Institute (NCI), the Centers for Disease Control and Prevention (CDC), the FDA, the American Medical Association (AMA), the American College of Surgeons (ACS), and the College of American Pathologists (CAP). [9]

The BI-RADS system includes categories or levels that are used to standardize interpretation of mammograms among radiologists. For referring physicians, the BI-RADS categories indicate the patient’s risk of malignancy and recommend a specific course of action.

Of all of the screening mammograms performed annually, approximately 90% show no evidence of cancer. On necessary further diagnostic testing, approximately 2% of all screening mammograms are shown to be abnormal and require biopsy. Among cases referred for biopsy, approximately 80% of the abnormalities are shown to be benign, and 20% are shown to be cancerous.

See Mammography in Breast Cancer for more information.

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