Accuracy of needle biopsy of breast lesions visible on ultrasound: Audit of fine needle versus core needle biopsy in 3233 consecutive samplings with ascertained outcomes

INTRODUCTION: Core needle biopsy (CNB) has progressively replaced fine needle aspiration cytology (FNAC) in the diagnosis of breast lesions. Less information is available on how these tests perform for biopsy of ultrasound (US) visible breast lesions. This study examines the outcomes of CNB and FNAC in a large series ascertained with surgical histology or clinical-imaging follow-up. MATERIALS AND METHODS: Retrospective five-year audit of 3233 consecutive US-guided needle samplings of solid breast lesions, from self-referred symptomatic or asymptomatic subjects, performed by six radiologists in the same time-frame (2003-2006): 1950 FNAC and 1283 CNB. The probability of undergoing CNB as a first test instead of FNAC was evaluated using logistic regression. Accuracy and inadequacy were calculated for each of CNB and FNAC performed as first test. Accuracy measures included equivocal or borderline/atypical lesions as positive results. RESULTS: The probability of CNB as a first test instead of FNAC increased significantly over time, when there was a pre-test higher level of suspicion, in younger (relative to older) women, with increasing lesion size on imaging, and for palpable (relative to impalpable) lesions. Inadequacy rate was lower for CNB (B1 = 6.9%) than for FNAC (C1 = 17.7%), p < 0.001, and specifically in malignant lesions (B1 = 0.9% vs. C1 = 4.5%; p < 0.001). False negative rate was equally low for both CNB and FNAC (1.7% each test). CNB performed significantly better than FNAC for absolute sensitivity (93.1% vs. 74.4%; p < 0.001) and complete sensitivity (97.4% vs. 93.8%; p = 0.001), however specificity was lower for CNB than FNAC (88.3% vs. 96.4%; p < 0.001). Absolute diagnostic accuracy was higher for CNB than FNAC (84.5% vs. 71.9; p < 0.001) while FNAC performed better than CNB for complete diagnostic accuracy (95.4% vs. 93.2; p < 0.008). In the small subgroup assessed with CNB after an inconclusive initial FNAC (231 cases) there was improved complete sensitivity (from 93.8% to 97.0%) however this also increased costs. CONCLUSION: FNAC and CNB were generally performed in different patients, thus our study reported indirect comparisons of these tests. Although FNAC performed well (except for relatively high inadequacy), CNB had significantly better performance based on measures of sensitivity, but this was associated with lower specificity for CNB relative to FNAC. Overall, CNB is the more reliable biopsy method for sonographically-visible lesions; where FNAC is used as the first-line test, inadequate or inconclusive FNAC can be largely resolved by using repeat sampling with CNB.