Microcalcifications of the breast: Size matters! A mammographic-histologic correlation study

Core needle biopsies (CNBs) of the breast are highly sensitive techniques for sampling of mammographic calcifications. Currently, there is no standardized protocol for evaluating such samples. This study was undertaken to attempt to standardize the procedure of correlating histologic findings with mammographically detectable calcification. 113 CNBs with mammographic evidence of calcification were first reviewed and histologically categorized into 2 main groups based on the presence or absence of microcalcifications. Biopsies with microcalcifications were divided into < 100 μm and ≥ 100 μm subgroups based on microcalcifications largest diameter either in aggregate or in isolation. Tissue blocks from discrepant biopsies (negative and < 100 μm microcalcifications) were radiographed. Deeper sectioning into the blocks was performed for discrepant biopsies. 102 of 113 CNBs (90.2%) had microcalcifications on primary review; 11 were negative and 21 had microcalcifications (< 100 μm) considered below the limit of mammographic detectability. Following tissue block radiology and deeper sectioning, large microcalcifications ≥100 μm were identified in 12 discrepant biopsies (1 negative and 11 < 100 μm). Without careful evaluation 10 discrepant biopsies would have been erroneously reported as "false" positive and one as "false" negative for microcalcifications. In conclusion, tissue block radiography and deeper sectioning is required to assess microcalcifications in all discrepant cases. We recommend a systematic approach to standardize reporting of microcalcifications in CNBs. Pathologists should routinely report the size of microcalcifications in their reports and correlate their findings with the tissue block radiologic findings. Discrepant "false-positive with < 100 μm microcalcifications" biopsies should be considered non-diagnostic and should be handled the same way as "negative" biopsies.