Measurements using mammography and ultrasonography underestimate the size of high-volume ductal carcinoma in situ.

BACKGROUND Surgical decisions for ductal carcinoma in situ (DCIS) are based on lesion sizes. This study aims to determine the accuracy of pre-operative imaging in estimating the size of DCIS. METHODS This was a retrospective review of clinicopathologic data of patients treated for DCIS with breast conserving surgery (BCS) between 2012 and 2018. Mammographic and sonographic lesion sizes were compared with final pathology sizes. RESULTS For the 152 lesions visible on mammography, mean size on imaging was significantly smaller when compared to final pathology (2.3 vs. 3.6 cm, p < 0.001). The mean difference of 1.3 cm was a significant underestimation with a correlation coefficient of 0.367 (p < 0.001). For 48 sonographically visible lesions, the radiologic size was significantly smaller than pathologic size (1.7 vs. 4.1 cm, p < 0.001), but the degree of underestimation was not significantly correlated (p = 0.379). CONCLUSION DCIS size was significantly underestimated by imaging. This must be taken into consideration during surgical planning.