The Breast Imaging Reporting and Data System: Positive predictive value of mammographic features and final assessment categories

OBJECTIVE. The purpose of the study was to assess the positive predictive value of mammographic features and final assessment categories described in the Breast Imaging Reporting and Data System (BI-RADS) for lesions on which biopsies have been performed. SUBJECTS AND METHODS. We prospectively evaluated 492 impalpable mammographically detected lesions on which surgical biopsy las opposed to percutaneous biopsy) was performed. Each lesion was classified according to BI-RADS descriptors for masses (margins and shape) and calcifications (morphology and distribution) and was categorized by the BI-RADS final assessment categories as category 3 ("probably benign"), category 4 ("suspicious abnormality"), or category 5 ("highly suggestive of malignancy"). Mammographic and pathologic findings were reviewed. RESULTS. Carcinoma was present in 225 (46%) of 492 lesions. For the 492 lesions subject to biopsy, BI-RADS final assessment categories were category 3 in eight lesions (2%), category 4 in 355 (72%), and category 5 in 129 (26%). The features with highest positive predictive Value for carcinoma were spiculated margins (81%), irregular shape (73%), linear calcification morphology (81%), and segmental or linear calcification distribution (74% and 68%, respectively). Carcinoma was present in 105 (81%) of 129 category 5 lesions compared with 120 (34%) of 355 category 4 lesions (p < .001). The frequency of carcinoma was higher in category 5 than in category 4 lesions for all mammographic lesion types and all interpreting radiologists. CONCLUSION. The standardized terminology of the BI-RADS lexicon allows quantification of the likelihood of carcinoma in an impalpable breast lesion. The features with highest positive predictive value-spiculated margins, irregular shape, linear morphology, and segmental or linear distribution-warrant designation of a lesion as category 5.