Malignancy Rates of Suspicious Breast Lesions in Patients on Annual Screening or Regular Follow-up Ultrasonography

PURPOSE: The objective of this study is to investigate the malignancy rates of BIRADS 4 and 5 lesions detected on annual screening or follow-up US and to correlate the malignancy rates with the rationales for biopsy. MATERIALS AND METHODS: Between 2010 and 2011, among 2837 patients who underwent US-guided core-needle biopsy, 423 patients underwent screening or regular follow-up US examinations. Lesions were classified into four groups: newly detected suspicious lesions, benign lesions with interval growth, benign lesions with suspicious changes of US features and benign lesions with interval growth and suspicious changes of US features. RESULTS: The malignancy rates were as follows: BI-RADS 4A low suspicion of malignancy, 8.1% (31/379); 4B intermediate suspicion of malignancy, 56% (14/25); 4C moderate suspicion of malignancy, 71.4% (10/14); 5 highly suggestive of malignancy, 100% (5/5). The malignancy rates for the four groups were as follows: newly detected suspicious lesions, 17.46% (51/292); benign lesions with interval growth, 7.77% (7/90); benign lesions with suspicious changes of US features, 4% (1/25); benign lesions with interval growth and suspicious changes of US features, 6.25% (1/16). Comparison of the malignancy rate of newly detected suspicious lesions with that of benign lesions with interval growth revealed a statistically significant difference (p=0.038). No significant differences were observed between the other groups (p>0.05). CONCLUSION: The malignancy rates of suspicious lesions detected on annual screening or follow-up US were similar to those of the reported BI-RADS data. A higher malignancy rate was observed for newly detected suspicious lesions than for lesions with interval growth.