Breast magnetic resonance imaging (MRI) is used to identify residual and additional disease in patients with invasive carcinoma. The use of MRI in assessing extent of disease for ductal carcinoma in situ (DCIS) is less well defined. This study assessed the value of MRI in the preoperative evaluation of DCIS.

We identified 98 patients with DCIS in 2007. Of these, 63 underwent stereotactic biopsy, followed by MRI. There were 35 who underwent stereotactic biopsy alone. Concordance between MRI and histopathology was defined as the presence or absence of residual disease.

There was no significant difference in mastectomy rates between the MRI and non-MRI group (20.3% vs 25.7%, P = .62). In patients undergoing breast-conserving surgery (BCS), there were fewer positive margins in the MRI versus the non-MRI group (21.2% vs 30.8%, P = .41). Of the 64 cases that underwent preoperative MRI, 43 (67.2%) were concordant. Also, 15 of 43 cases (34.8%) had MRI results that accurately predicted pathologic size. In 28 of 43 patients (65.2%), MRI overestimated disease in 20, by a mean of 1.97 cm. In patients with MRI tumor size >2 cm, MRI overestimated disease by a mean of 3.17 cm. Of the 64 cases, 21 (32.8%) were discordant. Also, 10 of 21 (47.6%) had a positive MRI and no residual disease on histopathology, and 11 of 21 (52.3%) had negative MRI and residual disease on pathology.

MRI does not accurately predict extent of disease in patients with extensive DCIS. In patients with MRI tumor size ≤2 cm, MRI may assist in surgical planning. MRI results in patients with DCIS should be interpreted with caution; decision for mastectomy should not be made on MRI findings alone.