*Correlation between 3T apparent diffusion coefficient values and grading of invasive breast carcinoma*

Purpose The aim of this study was to evaluate whether the apparent diffusion coefficient (ADC) provided by 3.0T (3T) magnetic resonance diffusion-weighted imaging (DWI) varied according to the grading of invasive breast carcinoma. Materials and methods A total of 92 patients with 96 invasive breast cancer lesions were enrolled; all had undergone 3T magnetic resonance imaging (MRI) for local staging. All lesions were confirmed by histological analysis, and tumor grade was established according to the Nottingham Grading System (NGS). MRI included both dynamic contrast-enhanced and DWI sequences, and ADC value was calculated for each lesion. ADC values were compared with NGS classification using the Mann–Whitney U and the Kruskal–Wallis H tests. Grading was considered as a comprehensive prognostic factor, and Rho Spearman test was performed to determine correlation between grading and tumor size, hormonal receptor status, HER2 expression and Ki67 index. Pearson's Chi square test was carried out to compare grading with the other prognostic factors. Results ADC values were significantly higher in G1 than in G3 tumors. No significant difference was observed when G1 and G3 were compared with G2. Tumor size, hormonal receptor status, HER2 expression and Ki67 index correlated significantly with grading but there was a significant difference only between G1 and G3 related to the ER and PR status, HER2 expression and Ki67 index. There was no statistically significant difference in lesion size between the two groups. Conclusion ADC values obtained on 3T DWI correlated with low-grade (G1) and high-grade (G3) invasive breast carcinoma. 3T ADC may be a helpful tool for identifying high-grade invasive breast carcinoma.