Objective To explore the diagnostic value of shear wave quality(SWQ) for two-dimensional shear wave elastography (2D-SWE) in the diagnosis of breast lesions with different sizes.Methods This prospective study was approved by the institution review board and informed consent was obtained from all the patients.From August 2014 to January 2015,243 patients with 260 pathologically proven breast lesions were included into this study.All patients underwent conventional ultrasound(US) and 2D-SWE examinations.According to the size, all breast lesions were divided into three groups (group one: ≤ 10mm,group two: 10 ~ 20mm,group three: ≥20mm) and then make an agreement.The evaluation of SWQ for 2D-SWE was as follow:if the SWQ images of breast lesions were in the whole green, the SWQs were regarded as good.On the contrary, if the images had yellow or/and red component, the SWQs were regarded as poor.The evaluation of SWQ were performed by two independent observers with difference experience of breast ultrasound diagnosis (one with 2-year experience and the other with 7-year experience).Lastly, in the three groups with different sizes,the comparisons of poor SWQ rates between benign and malignant breast lesions were performed (P< 0.05), respectively.And the Observer consistency was evaluated.Results In this study,63 (95.4%) breast lesions were confirmed by postoperative pathology and 8 (4.6%) breast lesions were proven by cytopathology.Pathologically, 192 (73.8%) breast lesions were confirmed as benign and 68 (26.2%) ones were confirmed as malignant.For all the breast lesions,the poor SWQ rate is 25.4% (66/260) with 38 (19.8%) in the benign breast lesions and 28 (41.2%) in malignant ones.For the benign breast lesions, the rates of poor SWQ were 6.3% (4/63), 21.4% (21/98) and 41.9% (13/31) for the group one, the group two and the group three, respectively.For the malignant breast lesions, the rates of poor SWQ were 10.0%(1/10),34.5%(10/29) and 58.6%(17/29) for the group one,the group two and the group three,respectively.There was significant difference of the poor SWQ rates between benign and malignant breast lesions for the group one and group two (Both P< 0.05),whereas there was no significant difference for group three (P=0.20).The Kappa value between the two observers for SWQ assessment was 0.837.Conclusion It is more suitable to use the SWQ from 2D-SWE for breast lesions with sizes less than or equal to 20 mm than for ones with sizes more than 20 mm in the diagnosis of breast carcinoma.