Objectives: This study aims to find the frequency and the malignancy rate of BI-RADS category 3 lesions detected on screening breast ultrasound and to evaluate whether they fullfilled the requirements of the latest American college of radiology imaging and reporting system.

Methods: Of 500 asymptomatic women who came to our center for screening sonography themselves or referred by their clinician, patients for whom BI-RADS category 3 lesions were seen on the ultrasound were selected. Clinical outcome of these lesions using one year follow up, biopsy or a combination of both were evaluated.

Results: The frequency of BI-RADS category 3 lesions detected on screening ultrasound was 18% (90/500). Of these patients, one was eventually proven to have malignancy with malignancy rate of 1.1%. This detected malignancy was early breast cancer with no lymph node metastasis.

Conclusions: Although the frequency of ultrasound BI-RADS category 3 lesions is considerably high (18 %), the malignancy rate is low (1.1%). Therefore careful assessment and follow up of BI-RADS category 3 can avoid unnecessary biopsy or surgery.

This is an abstract presented in the 33rd Iranian congress of radiology (ICR) and the 15th congress of Iranian radiographic science association (IRSA)