Many women age 40 and older undergo annual mammographic screening for early breast cancer, but what is the next step when the mammogram is abnormal? Should it be a needle biopsy, or are less invasive tests just as precise?

According to a recent review of the research by the Agency for Healthcare Research and Quality, after an abnormal mammogram, biopsy, either by needle sampling or surgical excision, is still the most accurate procedure for diagnosing breast cancer. Yet 80% of women who undergo tissue biopsy after an abnormal mammogram don't have breast cancer. Women who are at average risk for breast cancer would probably prefer a less invasive procedure, but the evidence shows that the less invasive procedures currently available, including magnetic resonance imaging, ultrasonography, positron emission tomographic scanning, and scintimammography, would miss between 38 and 93 cancers out of 1,000 cases.

Maryann Napoli, of the Center for Medical Consumers, agrees. "This report confirms longstanding medical advice that biopsy is a woman's best shot at accuracy," she says. "However, if I had a nonpalpable breast cancer diagnosed as a result of mammography, I would have a second pathologist examine the biopsy results because of the frequent confusion over differentiating between atypia hyperplasia and ductal carcinoma in situ (DCIS). And DCIS, which now represents 20% of all newly diagnosed breast cancers, does not always progress to a life-threatening disease. The key is distinguishing the ones with lethal potential."

The full report is available at http://effectivehealthcare.ahrq.gov/synthesize/reports/final.cfm?Document=4&Topi.