The role of diffusion-weighted imaging for differentiation of benign and malignant breast masses

Diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) measurements can, as is the case in many cases, provide valuable insight in differential diagnosis of breast lesions. The purpose of our study is to evaluate diagnostic accuracy of MRI, diffusion imaging and ADC values in differentiating benign and malignant breast masses. In this retrospective study, hospital and radiology department archives were examined between August 2010 and May 2014. 34 patients with breast mass visible in conventional MRI sequences, DWIs and ADC maps; and who had histopathologic diagnosis were included in the study. Tru-cut biopsy, vacuum biopsy or excisional biopsy was performed on the masses. Masses were classified according to BI-RADS depending on their shape, contour, enhancement and kinetic curves. Lesions were considered benign if they were categorized BI-RADS 2 and 3, and malignant if they were BI-RADS 4 or 5; and this was compared to histopathology results. ADC measurements were taken from masses and normal fibroglandular tissue. The relation between ADC values and histopathology results were statistically assessed. A cut-off value to differentiate benign and malignant breast masses was calculated using ROC analysis. Out of 34 breast masses in the study, 15 were benign and 19 were malignant according to histopathology. For purposes of malignancy detection, breast MRI was found to have a sensitivity of 100%, specificity of 40%, positive predictive value (PPV) of 67.9% and negative predictive value (NPV) of 100%. Histopathologically benign lesions had an ADC average (±SD) of 1.36±0.31 x 10-3 mm2/sn; malignant lesions lesions had an ADC average (±SD) of 0.89±0.17 x 10-3 mm2/sn; and normal fibroglandular tissue had an ADC average (±SD) of 1.65±0.24 x 10-3 mm2/sn. It was observed that malignant masses had ADC values lower than benign masses, and benign masses had values lower than normal fibroglandular tissue. By means of ROC analysis, an ADC cut-off value of 1.05 x 10-3 mm2/sn was found, with a sensitivity of 95%, specificity of 87%, PPV of 90 % and NPV of 93% for detection of malignancy. When breast masses are evaluated with MRI, both morphological and kinetic parameters are considered. However, morphological characteristics and contrast enhancement patterns of benign and malignant lesions can be similar, and thus, these may perform inadequately to discriminate benign masses from malignant ones. In the literature, conventional breast MRI is reported to have a sensitivity of 90%, but its specifity is reported in a wide range of 37-97%. DWI can provide information related to cellularity of the lesion and thus can be a useful addition to conventional MRI for lesion characterisation. Very rapid and easy acquisition of images and the lack of contrast media are the advantages of DWI; however it is very sensitive to artifacts and has low sensitivity for small lesions due to low spatial resolution. We think DWI can have routine application in breast MRI if its image quality is improved Key words: Breast, MRI, ADC, mass.