Probably benign breast lesions on ultrasonography: A retrospective review of ultrasonographic features and clinical factors affecting the BI-RADS categorization

Background: The retrospective review of probably benign lesions on mammograms is well investigated. Although suspicious malignant ultrasonography (US) features have been detected on retrospective reviews of US examinations, the review of probably benign lesions on US is rarely studied. Purpose: To investigate how many probably benign lesions on US fulfilled the published criteria and to evaluate how clinical and personal factors influenced the categorization of breast lesions. Material and Methods: A total of 920 nodules in 920 women with more than 24 months follow-up after the initial category 3 assessment on US or excision were included. We retrospectively reviewed the initial US images according to previously published criteria, and evaluated several factors that could influence the characterization of breast lesions in clinical practice such as age, multiplicity, palpability, radiologist's experience, and lesion size. Results: Of 920 lesions, 906 (98.5%) were benign and 14 (1.5%) were malignant. Of 920 lesions, 376 (40.9%) including 13 malignancies were reassessed as category 4. If strict criteria had been applied at initial US examination, the positive biopsy rate would have been only 3.5% (13/376) and 96.5% (363 of 376) biopsies would have been unnecessary. Lesions in women 40 years or older and multiple lesions were more frequently reassessed as category 4 (P<0.00 and P=0.01, respectively). The presence of palpability, lesion size, and the radiologist's experience did not significantly influence the categorization of breast lesions on US. Of 920 probably benign lesions, 40.9% could be classified as category 4 lesions when strict criteria were applied in initial practice. Conclusion: The multiplicity of the lesion and the patient's age were found to have a significant influence on the classification of probably benign solid masses.