Objective To summarize the characteristics of BI-RADS 4a breast diseases under ultrasonic examination referring to patients' clinical data and pathological reports.Methods 82 patientswho were firstlydiagnosed and treated in the Affiliated Hospital of Jiangnan University were included.The ultrasonograms were retrospectively reviewed along with the correlated pathological and clinical findings.Results 48 (58.5%) cases were benign,among which fibroadenoma was the most common.34 cases (41.4%) were malignant,among which invasive ductal carcinoma was the most common.68 of the 82 cases were neoplastic disease (82.9%),6 (9.8%)were inflammatory disease,and 8(7.3%) were adenosis.Conclusions The patientswho are graded BI-RADS 4a by ultrasonic examination may have completely different diseases.Beyond the most common benign diseases,few of them are malignancies with atypical,even ambiguous sonographic features.Therefore,in clinical practice,sonologists should set appropriate parameters of ultrasonicdevices appropriately,and evaluate the sonographic features carefully,in order to make the correct grading and diagnosis.While for clinicians,it is necessary to learn to read the ultrasonographic features along with patients' manifestations,and finally reduce the misdiagosis and missed diagnosis of such diseases.