The diagnostic dilemma with the plateau pattern of the time-intensity curve: can the relative apparent diffusion coefficient (rADC) optimise the ADC parameter for differentiating breast lesions?

AIM To assess the performance of the apparent diffusion coefficient (ADC) and relative ADC (rADC) to differentiate benign from malignant breast lesions using the plateau pattern of the time–intensity curve (Type II TIC), including the impact of lesions-enhancement subtypes and menopausal status of patients. MATERIALS AND METHODS Between September 2016 and December 2019, 408 patients with 169 benign and 239 malignant lesions with Type II TIC underwent magnetic resonance imaging (MRI), including diffusion-weighted imaging, with b-values of 50 and 800 s/mm2. ADC and rADC values were calculated by placing regions of interest (ROIs) on the lesion, the parenchyma of the normal breast, and the pectoralis major muscle. A receiver operating characteristic (ROC) curve was generated to compare the diagnostic performance of each parameter in distinguishing between benign and malignant breast lesions. Further classification was undertaken to study the discriminatory performance of each parameter in the different lesions enhancement subtypes (mass-like enhancement [MLE] and non-MLE [NMLE]) and menopausal status of patients (pre-menopausal and post-menopausal). RESULTS There was a significant difference in the ADC and rADC values between benign and malignant lesions. The sensitivities of lesion ADC, gland rADC, and muscle rADC were 79.29%, 77.51%, and 79.29%, respectively, with specificities of 94.56%, 82.01%, and 94.98%, respectively. The area under the ROC curve (AUC) of muscle rADC was the highest (AUC=0.92), especially in the MLE subtype (AUC=0.96), and was not affected by the menopausal status. CONCLUSION Muscle rADC and lesion ADC assessment improved the diagnostic performance of breast MRI in distinguishing between benign and malignant breast lesions with Type II TIC, especially muscle rADC in the MLE subtype.