Interobserver concordance in the BI-RADS classification of breast ultrasound exams

Breast ultrasound is an important complement to the clinical/mammographic investigation of breast lesions. This operator-dependent method entails real-time image detection and analysis and requires extensive training and experience in identifying and differentiating between benign and malignant lesions (1-4). Lesion contour and shape are considered to be the main features that allow differentiating benign and malignant lesions, the former with high sensitivity and the latter with high specificity. Many authors believe that combined ultrasound methods may yield greater accuracy (5-10). However, using morphological characteristics for lesion differentiation demands a high rate of interobserver agreement, an issue that has been extensively examined for mammography but that has been given less attention for ultrasound. Interobserver agreement is thus a matter of strong concern in clinical radiological practice (3-11). To better characterize the interobserver agreement in breast ultrasound, this study examined a group of 14 breast imagers who used the Breast Imaging Reporting and Data System (BI-RADS) ultrasound classification on 40 breast lesions. The study was exclusively concerned with lesion categorization agreement among the observers according to the BI-RADS lexicon. The accuracy of the observers was not directly assessed through comparisons with the final lesion histology.