Background Idiopathic granulomatous mastitis (IGM) is a chronic, unpleasant autoimmune inflammatory condition and is clinically and radiologically often confused with breast malignancy. Purpose To investigate the contributions of qualitative and quantitative aspects of acoustic radiation force impulse (ARFI) elastography to the differential diagnosis between IGM and invasive ductal carcinoma (IDC) in the breast. Material and Methods Ninety-four women with IDC and 39 with IGM were included in the study. Shear wave velocity (SWV) was calculated for all lesions using quantitative elastography. Next, each lesion's correspondence on qualitative elastographic images to those on the B-mode images was evaluated: pattern 1, no findings on elastography images; pattern 2, lesions that were bright inside; pattern 3, lesions that contained both bright and dark areas; and pattern 4, lesions that were dark inside. Pattern 4 was subdivided into 4a (dark area same size as lesion) and 4b (dark area larger than lesion size). Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were calculated. Results The mean SWV based on ARFI elastography was 3.78 +/- 1.26 m/s for IGM and 5.34 +/- 1.43 m/s for IDC lesions (P < 0.05). Based on qualitative ARFI elastography, IDC lesions were mostly classified as pattern 4b, while IGM lesions were mostly classified as pattern 1 or 2 (P = 0.01). Evaluation of both the qualitative and quantitative aspects of ARFI elastography yielded a sensitivity of 89% and specificity of 84%. Conclusion ARFI elastography may facilitate the differential diagnosis between IGM and IDC.