Single focus on breast magnetic resonance imaging: diagnosis based on kinetic pattern and patient age

Background Because of its small size, a focus in breast magnetic resonance imaging (MRI) must be evaluated on the basis of characteristics other than morphologic features. Patient-related factors including patient age, in conjunction with lesion-related factors, could be useful for decision-making. Purpose To assess the probability of malignant foci based on both lesion- and patient-related factors, and to propose a relevant decision-making method. Material and Methods Foci in our breast MRI database dating from April 2006 to June 2013 were retrospectively identified and analyzed. A Fisher's exact test or a Mann-Whitney U test were performed for univariate analyses, and factors that showed a significant association with outcome in the univariate analyses were subjected to multivariate analysis using a logistic regression model. A decision tree was then drawn using the significant predictors confirmed by multivariate analysis. Results In total, 184 foci (168 benign, 16 malignant) in 184 patients were analyzed in our study. The presence of a washout pattern and older age were found to be significant predictors of malignancy ( P < 0.0001; odds ratio [OR], 17.8; P = 0.021; OR, 1.1, respectively). The main decisive node on the decision tree was the presence of a washout pattern, followed by whether the patient's age was >63 years. Conclusion An enhancing focus showing a washout pattern, especially in older patients, may warrant immediate biopsy rather than short-interval follow-up.