Magnetic resonance imaging (MRI) as compared to mammogram (MMG) in the evaluation of size, number of lesions, and nodal positivity in breast cancer (BrCa).

1102 Background: Direct comparison between MRI and MMG for accuracy of size of the lesion or nodal status in BrCa is lacking. We aim to analyze MMG and MRI findings for nodal status and size of the lesion compared with pathology as a gold standard. Methods: A retrospective analysis was performed on patients (pts) with BrCa who had MRI and MMG. Pts who had excisional biopsy prior to MRI or neoadjuvant therapy were excluded. The number and size of lesions detected by MMG and MRI were compared to pathology. Nodal positivity of pts with additional malignant lesions detected by MRI only was compared to nodal positivity of single lesions detected by MRI and MMG. Results: Between 2003-2010, 318 pts, 414 lesions were identified by MMG and/or MRI. Out of 414 lesions, 210 lesions were detected by MRI and MMG, and size was available to compare to pathology. Out of 210 lesions, MRI overestimated (OE) 56% of lesions by an average of 1.0 cm, MMG underestimated (UE) the same lesions in 53% by an average of 0.6 cm and 9%...