Objective To explore the value of shear wave elastography（SWE）combined with breast imaging reporting and data system（BI-RADS） classification in the differential diagnosis of breast cancer with a maximum diameter ≤2 cm（hereinafter referred to as small breast cancer）.Methods A total of 177 small breast lesions（maximum diameter ≤2 cm）were selected from 171 patients with breast lesions confirmed by pathology

among which 155 were benign and 22 were malignant.Preoperative BI-RADS classification and SWE were performed to obtain maximum elasticity value（Emax）

average elasticity value（Emean）

minimum elasticity value（Emin）and standard deviation（Esd）

the differences between benign and malignant lesions were compared.The receiver operating characteristic（ROC）curve was drawn to determine the diagnostic critical value of Emax

and the BI-RADS classification was adjusted according to the Emax of category 4 a lesions. The diagnostic efficacy of SWE and BI-RADS classification alone and in combination for BI-RADS 4 a lesions was compared.Results Among the 177 lesions

BI-RADS classification showed 57 lesions were category 3

94 lesions were category 4 a

13 lesions were category 4 b

8 lesions were category 4 c

and 5 lesions were category 5. Emax

Emean

Emin and Esd were significantly higher in malignant compared with benign lesions（all P<0.05）.By using cutoff of Emax 87.5 Kpa for downgrading BI-RADS category 4 a lesions to category 3

71 category 4 a lesions were downgraded and 5 cancers were missed.The sensitivity

specificity

accuracy and the area under the ROC curve of Emax combined with BI-RADS in the diagnosis of small breast cancer were 77.3%

82.6%

79.1% and 0.861（95%CI:0.801～0.909）

there were statistically significant differences compared with those of BI-RADS classification alone（all P<0.05）.Conclusion Compared with the BI-RADS classification alone

the combined application of SWE can improve the specificity and accuracy in the diagnosis of small breast cancer

and reduce the unnecessary puncture and surgery for 4 a lesions in the clinical diagnosis and treatment

with good application value.