MRI-only lesions: application of diffusion-weighted imaging obviates unnecessary MR-guided breast biopsies.

OBJECTIVE

To assess if the application of diffusion-weighted imaging (DWI) obviates unnecessary MR-guided biopsies in suspicious breast lesions visible only on contrast-enhanced MRI (CE-MRI).

METHODS

This institutional review board (IRB)-approved, retrospective, single-centre study included 101 patients (mean age, 49.5; SD 13.9 years) who underwent additional DWI at 1.5 T prior to MRI-guided biopsy of 104 lesions classified as suspicious for malignancy and visible on CE-MRI only. An experienced radiologist, blinded to histopathologic and follow-up results, measured apparent diffusion coefficient (ADC) values obtained from DWI. Diagnostic accuracy was investigated using receiver operating characteristics (ROC) analysis.

RESULTS

Histopathology revealed 20 malignant and 84 benign lesions. Lesions were masses in 61 (15 malignant, 24.6 %) and non-masses in 43 cases (five malignant, 11.6 %). Mean ADC values were 1.53 ± 0.38 × 10(-3) mm(2)/s in benign lesions and 1.06 ± 0.27 × 10(-3) mm(2)/s in malignant lesions. ROC analysis revealed exclusively benign lesions if ADC values were greater than 1.58 × 10(-3) mm(2)/s. As a consequence, 29 false-positive biopsies (34.5 %) could have been avoided without any false-negative findings. Both in mass and in non-mass lesions, rule-in and rule-out criteria were identified using flexible ADC thresholds based on ROC analysis.

CONCLUSION

Additional application of DWI in breast lesions visible only on MRI can avoid false-positive, MR-guided biopsies. Thus, DWI should be an integral part of breast MRI protocols.

KEY POINTS

DWI measurements are a fast and helpful technique for improved breast lesion diagnosis. DWI application in breast lesions visible only on MRI obviates false-positive, MR-guided biopsies. Flexible ADC thresholds provide rule-in and rule-out criteria for breast lesion malignancy.