Additional diagnostic value of lesion visibility on diffusion-weighted imaging for differentiating BI-RADS category 4...

This study aimed to evaluate whether adding diffusion-weighted imaging (DWI) to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) improves the differentiation between nonmalignant and malignant MRI-detected lesions.

A total of 36 patients with 40 Breast Imaging-Reporting and Data System (BI-RADS) category 4 MRI-detected lesions were analyzed. Two readers independently evaluated lesion visibility on two b-value DWIs (b = 800 s/mm², DWI₈₀₀ and b = 1500 s/mm², DWI₁₅₀₀) using a five-point scale (from 0 = poor to 4 = excellent) and measured the apparent diffusion coefficient (ADC) values. DWI visibility scores and ADC values were compared between nonmalignant and malignant lesions. For the diagnostic performance analysis, lesions were classified as DWI-positive (scores 2-4, suggestive of malignancy) or DWI-negative (scores 0-1, suggestive of benignity).

The inter-observer agreement of the DWI visibility score was substantial for both DWI₈₀₀ (κ = 0.923) and DWI₁₅₀₀ (κ = 0.864). The lesion visibility score was higher on DWI₁₅₀₀ than on DWI₈₀₀. The score was significantly higher for malignant than for nonmalignant MRI-detected lesions on both DWI₈₀₀ (reader 1: 2.74 vs. 1.57, p = 0.012; reader 2: 2.95 vs. 1.81, p = 0.020) and DWI₁₅₀₀ (reader 1: 3.11 vs 2.24, p = 0.048; reader 2: 3.00 vs. 1.95, p = 0.038). For mass lesions, both DWI₈₀₀ and DWI₁₅₀₀ achieved 100% sensitivity and a negative predictive value for both readers, whereas all DWI-negative malignant lesions demonstrated non-mass enhancement. Overall, the mean and minimum ADC values did not differ significantly between nonmalignant and malignant lesions.

The present findings suggest that DWI visibility provides additional value for distinguishing between nonmalignant and malignant BI-RADS category 4 MRI-detected breast lesions. Particularly for mass lesions, DWI-negative MRI-detected lesions were associated with nonmalignant pathology, indicating a potential role for DWI in reducing unnecessary biopsies.