In each patient, bilateral whole breast sonography was performed in the transverse and longitudinal planes using a Siemens Acuson Antares 5.0 US scanner equipped with 7.5-13.0MHz liner-array transducer. Sonographic features of lesions (size, shape, margin, internal echogenicity, presence/absence of calcification, posterior acoustic phenomena, anterior posterior-width ratio, and presence/ absence of lymph node enlargement, presence/absence of intra-tumoral blood flow) were prospectively recorded in a computer database system. With these features they were classified to BIRADS lexicon by single observer (XZ), who had 15 years of experience on breast sonography