Evaluation of Malignancy Risk Stratification of Microcalcifications Detected on Mammography: A Study Based on the 5th Edition of BI-RADS

Background: The 5th edition of Breast Imaging Reporting and Data System subdivides suspicious calcifications into two categories: 4B—amorphous, coarse heterogeneous, and fine pleomorphic calcifications; 4C—fine linear or fine linear branching calcifications. We investigated whether these revised categories are appropriate for malignancy risk stratification. Methods: We studied 246 patients (mean age 48.2 years) with suspicious microcalcifications detected on mammography who underwent stereotactic biopsy (n = 154) or surgical excisional biopsy with preoperative mammogram-guided needle localization (n = 92). Pre-biopsy mammograms were reviewed retrospectively, and imaging features were analyzed according to the revised morphology and distribution descriptors. Pathological results of stereotactic biopsy and surgical excision were considered, with the surgical results being the reference standard. Positive predictive values (PPVs) were calculated and compared using the χ² test or Fisher’s exact test. Results: Overall PPV of suspicious microcalcifications was 22.4 %. PPVs of morphology descriptors were as follows: amorphous 7.9 %, coarse heterogeneous 17.8 %, fine pleomorphic 63.2 %, fine linear/fine linear branching 100 % (p < 0.001). PPVs of distribution descriptors were as follows: regional 8.8 %, grouped 14.3 %, linear 87.5 %, segmental 63.6 % (p < 0.001). For morphology and distribution descriptors combinations, PPVs for amorphous/regional and amorphous/grouped microcalcifications were 4.2 and 7.6 %, resepectively. The PPV for fine pleomorphic/linear or segmental was 93.8 %. Conclusions: Subcategorization of morphology descriptors for suspicious microcalcifications is needed because of the different PPVs for amorphous, coarse heterogeneous, and fine pleomorphic microcalcifications. Combining morphology and distribution descriptors for suspicious microcalcifications provides accurate risk stratification.