Objective: To compare the efficacy of three conventional imaging tests, mammography (MG), ultrasonography (US), and magnetic resonance imaging (MRI), in assessing the size of ductal carcinoma in situ (DCIS) or ductal carcinoma with microinvasion (DCIS-MI) lesions in breast-conserving patients. The efficacy of three conventional imaging tests, US and magnetic resonance imaging (MRI), in assessing the size of ductal carcinoma in situ (DCIS) or ductal carcinoma in situ with microinvasion (DCIS-MI), and the potential value of these tests in assisting the clinical management of breast-conserving patients.Methods: Retrospectively collected data from pathologically confirmed DCIS/DCIS-MI cases in our hospital were analyzed. The lesion sizes estimated by the three imaging modalities were compared with the "gold standard" pathological sizes. McNemar"s test and Bland-Altman plots were used to evaluate the accuracy and consistency of the different imaging methods. Univariate and multivariate analyses were performed to identify clinical,