Diagnosis of breast cancer: contribution of US as an adjunct to mammography.

PURPOSE: To determine the value of ultrasonography (US) as an adjunct to mammography for the diagnosis of breast cancer. MATERIALS AND METHODS: In a 2-year prospective study, 4,811 mammograms were classified according to level of suspicion of malignancy. Targeted US was performed to analyze (a) circumscribed lesions, possibly cysts; (b) palpable lesions visible at mammography; (c) palpable lesions not visible at mammography; and (d) nonpalpable lesions visible at mammography. After US was performed in 1,103 cases (23%), cases were reclassified for level of suspicion. RESULTS: In 338 cases, breast cancer was diagnosed. The sensitivity of mammography for all 4,811 cases was 83%; the specificity was 97%. After US, the combined sensitivity increased to 91%, with a specificity of 98%. The increase was significant (P < .001). The increase in sensitivity was highest among women younger than 50 years. The positive predictive value for mammography was high (72%), which reflects a high threshold for biopsy; this may have augmented the yield of US. CONCLUSION: The use of US as an adjunct to mammography resulted in an increase in diagnostic accuracy. Its contribution to the diagnosis of breast cancer in this study was 7.4%.