ABSTRACT
Objective To study the interobserver variabilities and the differential diagnosis value of Breast Imaging Reporting and Data System-Ultrasound (BI-RADS-US) lexicon for small ( ≤ 2 cm) breast nodules. Methods Between January 2009 and December 2011, 289 patients with small (≤2 cm) breast nodules (n=317) were included. According to sizes, the lesions were divided into two groups, i.e., 0-1 cm (n=160) group and 1-2 cm (n=157)group. Each lesion was described independently by 3 radiologists using BI-RADS-US lexicon. Interobserver variabilities were assessed by Kappa test. Chi-square test was used to compare the frequency difference of the descriptors between malignant and benign lesions. Sensitivity, speciifcity, accuracy, positive predictive value and negtive predictive value were calculated. Results (1)Moderate agreements were obtained for lesion shape, orientation, margin, echo pattern, surrounding tissue and calciifcations (κ=0.44, 0.57, 0.48, 0.43, 0.51 and 0.57) in 0-1 cm group. Substantial agreements were obtained for lesion shape, orientation, margin and echo pattern (κ=0.65, 0.61, 0.64 and 0.63) in 1-2 cm group. (2)Irregular shape, non-parallel orientation, non-circumscribed margin, echogenic halo and microcalciifcations were more frequently found in malignant nodules than in benign nodules in 0-1 cm group [52.3% (34/65) vs 20.0% (19/95), 38.5%(25/65) vs 13.7%(13/95), 75.4%(49/65) vs 32.6%(31/95), 18.6%(12/65) vs 0 (0/95) and 10.8%(7/65) vs 2.1%(2/95);χ2=18.19, 13.08, 28.22, 16.39 and 3.95;P=0.000, 0.000, 0.000, 0.000 and 0.047]. Similarly, irregular shape, non-parallel orientation, non-circumscribed margin, echogenic halo, shadowing, changes of Cooper′s ligament and microcalciifcations were signiifcantly more frequent found in malignant nodules than in benign nodules in 1-2 cm group [74.2%(49/66) vs 12.1%(11/91), 36.3%(24/66) vs 5.5%(5/91), 93.9%(62/66) vs 22.0%(20/91), 37.9%(25/66) vs 3.3%(3/91), 30.3%(20/66) vs 7.7%(7/91), 15.2%(10/66) vs 0 (0/91) and 16.7%(11/66) vs 4.4%(4/91);χ2=62.59, 24.21, 79.40, 31.22, 13.73, 12.30 and 6.67;P=0.000, 0.000, 0.000, 0.000, 0.000, 0.000 and 0.010]. (3)In both groups, a good sensitivity was demonstrated (75.4%&93.9%) when using the non-circumscribed margin as a criterion for malignancy, and high speciifcity was achieved in two groups (80.0%-100%and 87.9%-100%) when other descriptors including irregular shape, non-parallel orientation, echogenic halo, shadowing, changes of Cooper′s ligament and microcalciifcations were used as differentiation criteria. Conclusions Good interobserver agreement can be achieved using the BI-RADS-US lexicon in the diagnosis of small breast nodules. Non-circumscribed margin are proved as the most valuable sign for screening malignant breast lesions ≤ 2 cm. High speciifcity was found for irregular shape, nonparallel orientation, echogenic halo, shadowing, Cooper′s ligament changes and microcalciifcations, which can help biopsy and preoperative diagnosis.