ABSTRACT
PURPOSE: The aim of our study was to evaluate the outcomes of sonographic (US) BIRADS category 4 lesions according to subcategories 4A, 4B, and 4C and palpability. MATERIALS AND METHODS: We retrospectively reviewed the pathology results of 512 US BI-RADS category 4 lesions in 460 patients after ultrasound-guided percutaneous biopsy (n = 435) and surgical biopsy (n = 77). We analyzed the results according to subcategories 4A, 4B, 4C, and palpability, and compared outcomes of five breast radiologists. RESULTS: In BI-RADS 4A lesions (n = 302), biopsy results indicated 48 malignancies (15.9%). In BI-RADS 4B lesions (n = 113), biopsy revealed 69 malignancies (61.1%). Among BI-RADS 4C lesions (n = 97), 87 lesions were malignancies (89.7 %). Palpability had no correlation with the rate of malignancy in BI-RADS category 4 lesions, and the rate of malignancy for category 4A ranged widely from 8.1% - 26.4%. CONCLUSIONS: The outcomes of US BI-RADS category 4 lesions according to subcategories varied widely between radiologists, especially for 4A lesions. The US finding itself warrants a BI-RADS 4 subcategory. In category 4 lesions, the malignant rate was the same between palpable and nonpalpable lesions.