Preoperative breast MRI: reproducibility and significance of findings relevant to nipple-areolar complex involvement

Background: Eligibility of nipple-sparing mastectomy has been expanded. The purpose of this study was to evaluate interobserver agreement regarding magnetic resonance imaging (MRI) descriptors important in determining eligibility for mastectomy, and to investigate the significance of enhancement extending to the areola concerning nipple-areolar complex (NAC) involvement.

Methods: Fifty-one cases with histologically confirmed NAC involvement and 54 cases with negative NAC were enrolled. Two radiologists assessed the following factors: lesion morphology (mass or non-mass enhancement); intra-nipple bright signal; enhancement extending to the areola; abnormal nipple enhancement; and tumor-nipple distance. Factors that showed a significant association with outcome in the univariate analysis were assessed by means of multivariate analysis using a logistic regression model. Interobserver agreement between observers was assessed by calculating κ values (dichotomous variables), or intraclass correlation coefficients (ICCs; continuous variables).

Results: In multivariate analysis of the results from the two observers, tumor-nipple distance (observer 1: odds ratio [OR] 0.93; 95% confidence interval [CI] 0.88-0.99; observer 2: OR 0.89; 95% CI 0.83-0.95) and enhancement extending to the areola (observer 1: OR 17.9; 95% CI 1.97-162.2; observer 2: OR 24.0; 95% CI 2.62-219.7) were found to be significant predictors of NAC involvement. A substantial agreement (κ = 0.64-0.71) for every dichotomous variable and an almost perfect agreement (ICC = 0.86) for continuous variable were observed.

Conclusions: Findings of breast MRI for NAC preservation had good interobserver agreement. Enhancement extending to the areola, together with tumor-nipple distance, was significant factors for NAC involvement.