Diffusion-weighted imaging in breast cancer: Relationship between apparent diffusion coefficient and tumour aggressiveness

Aim: To assess the utility of diffusion-weighted imaging in diagnosing and characterizing breast malignancy. Materials and methods: From April 2006 to April 2009, all consecutive patients with breast cancer undergoing breast magnetic resonance imaging (MRI) and subsequent surgery in our hospital were enrolled in this study. MRI was performed using a 1.5 T MRI unit using a dedicated, bilateral, four-channel breast coil. The MRI protocol included a diffusion sequence acquired using b values of 0 and 1000 s/mm2. For each malignant lesion the relationships between tumour grade and histology and the relative value of the apparent diffusion coefficient (ADC) were analysed. Results: There were 136 female patients with 162 lesions. Histology revealed 149 invasive carcinomas and 13 ductal carcinomas in situ. There were 34 grade 1, 61 grade 2, and 67 grade 3 lesions. The mean ADC value of all malignant lesions was 1.03 × 10-3 mm2/s. The mean ADC values for invasive and in situ carcinomas were 1.03 × 10-3 mm 2/s and 1.05 × 10-3 mm2/s, respectively. The mean ADC values for grade 1, 2, and 3 tumours were 1.25 × 10 -3 mm2/s, 1.02 × 10-3 mm2/s, and 0.92 × 10-3 mm2/s, respectively. A statistically significant (p < 0.001) inverse correlation was disclosed between the ADC value and the tumour grading. The mean ADC value of the "less aggressive" group of disease (G1 and in situ lesions) was 1.19 × 10-3 mm2/s, whereas the mean ADC value of the "more aggressive" group (G2-G3 invasive carcinomas) was 0.96 × 10 -3 mm2/s (p < 0.001). Conclusion: The study confirms the usefulness of diffusion imaging in assessing the aggressiveness of breast tumours. ADC appears to be a promising parameter in the evaluation of the degree of malignancy of breast cancer tissue. © 2010 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.