Analysis of breast imaging reporting and data system category 4 complex cystic masses of the breast: Do all the complex cystic breast masses merit a biopsy?

To investigate whether sonographic findings can predict malignancy in complex echoic breast masses using the Breast Imaging Reporting and Data System (BI-RADS) lexicon and to demonstrate the need for biopsy recommendations for all complex breast masses. 135 pathologically proven complex echoic masses detected on sonography were identified. We retrospectively reviewed the sonographic findings according to the BI-RADS lexicon which include shape, margin, orientation, lesion boundary, posterior acoustic features, and vascularity. The sonographic findings were correlated with the pathology and mammographic findings. Differentiation between the sonographic appearance of benign and malignant complex cystic lesions was evaluated using the chi-square test or the Mann-Whitney U test. 59.3% (80/135) were benign lesions and 40.7% (55/135) were malignant lesions. Malignant lesions were correlated with irregular (p < 0.001), nonparallel (p = 0.023), noncircumscribed (p < 0.001), echogenic halo (p < 0.001), increased vascularity (p = 0.001) and large size (p = 0.002) compared to benign lesions. However, 12.7% (7/55) of benign looking complex cystic masses were proved to be malignant. All seven lesions had malignant microcalcifications or abnormality on mammography. Using the sonographic BI-RADS lexicon can be useful for differentiating between malignant and benign complex cystic breast masses. Notably, 12.7% of the complex cystic lesions showing a benign appearance on sonography were pathologically proven malignant. Therefore, radiologist should recommend biopsy for complex cystic lesions.