The ACR BI-RADS® 4th edition provides little guidance on how to classify microcalcifications depicted on mammogram into final assessment categories. We retrospectively evaluated whether our categorization could predict the probability of malignancy, based on histopathology and imaging follow-up.

From 2004 to 2005, 83 women who underwent image-guided biopsy for suspicious microcalcifications were subjected. Each lesion was classified by the final assessment categories as category 3 (probably benign finding), category 4A (low suspicion of malignancy), category 4BC (intermediate to moderate suspicion of malignancy), and category 5 (highly suggestive of malignancy) according to our criteria. The positive predictive value (PPV) of each category was assessed.

The final assessment categories were category 3 in 4 cases (4.8%), category 4A in 40 cases (48.1%), category 4BC in 31 cases (37.3%), and category 5 in 8 cases (9.6%). The PPVs for malignancy were 0% in C3, 7.5% in C4A, 64.5% in C4BC and 87.5% in C5.

Our categorization correlated well with the suggested probability of malignancy in the BI-RADS. It is thought that the application of the subcategories, 4A and 4BC, is of help to stratify the probability of malignancy of lesions requiring biopsy.