Evaluating the Impact of Breast Density on Preoperative MRI in Invasive Lobular Carcinoma.

BACKGROUND The focus of this study was to assess the accuracy of breast MRI in predicting pathologic tumor size in invasive lobular carcinoma (ILC) and to evaluate the incidence and factors associated with the detection of additional MRI lesions in ILC patients. STUDY DESIGN We retrospectively reviewed data from patients with stage I to III ILC diagnosed between 2010 and 2016 at our institution. Univariable and multivariable logistic regression were used to determine factors associated with detection of additional suspicious lesions on MRI. RESULTS The cohort included 99 women with ILC who underwent preoperative MRI, with a median age of 61 years (range 35 to 80 years). The sensitivity of MRI for detecting invasive lobular carcinoma was 99%, higher than that of mammography (68%) and ultrasound (92%). Mammography and ultrasound had a tendency to underestimate ILC, and MRI estimates of final tumor size were concordant in the majority (58.6%) of cases, with a median discordance of -2 mm. Magnetic resonance imaging detected additional ipsilateral malignancy in 23.2%, occult contralateral disease in 3.0%, and altered surgical management in 29.3% of ILC cases. In multivariable analyses, factors significantly associated with additional suspicious findings on MRI included higher breast density (odds ratio 3.19; 95% CI 1.01 to 10.0) and lymph node-positive disease (odds ratio 4.02; 95% CI 0.96 to 16.9). CONCLUSIONS Preoperative MRI is a useful adjunct to conventional breast imaging in ILC, particularly in women with dense breast tissue.