OBJECTIVESThe purpose of this study was to assess the incremental value of preoperative breast MRI over mammography and US in depicting the accurate extent of disease in invasive duct carcinoma (IDC) compared to invasive lobular carcinoma (ILC). PATIENTS AND METHODSRetrospective analysis of pre-operative mammography, US and MRI was performed in 239 patients with either IDC (n = 193) or ILC (n = 46). Images were evaluated for solitary, multifocal or multi centric disease and compared for concordance with postsurgical pathology. Discordance was documented as either overestimation or underestimation. Two tailed paired T and Fischer's exact tests were used for analysis. RESULTSMultifocality was present on pathology in 35% and 61% of patients with IDC and ILC (P < .05) and multicentricity in 23% and 41% respectively (P = .84). In ILC, MRI demonstrated better concordance with pathology compared to mammography and US (89%, 44%, 49% for multifocality P < .05 and 80.5%, 63%, 71% for multicentricity P = .3). For IDC, concordance with pathology for all modalities was similar (65%-76%). Among discordant cases, underestimation was significantly more common for mammography and US, while MRI more frequently overestimated disease extent. MRI very rarely overestimated multifocal disease in ILC (2%). CONCLUSIONMRI demonstrates an 80% to 90% concordance rate with pathology for ILC, superior to mammography and US. The addition of MRI in IDC patients may decrease underestimation of disease extent and potentially contribute to a reduction in post-operative residual disease.