目的 探讨超声引导下细针穿刺抽吸活检（US-FNAB）对甲状腺超声影像报告和数据系统（TI-RADS）4类甲状腺结节的诊断价值。方法 回顾性分析在上海交通大学医学院附属瑞金医院接受US-FNAB检查的甲状腺患者的术前超声特征，根据TI-RADS评估每个结节的恶性风险并进行分类，将其中TI-RADS 4a、4b和4c类共265例患者的281个结节纳入为可疑结节，所有结节均行US-FNAB检查，排除细胞学无相关诊断（不满意）结果的病例，将入组的274个结节的US-FNAB细胞学诊断结果与病理结果或随访结果进行对照研究。结果 281个TI-RADS 4类结节中，细胞学诊断恶性97个，可疑恶性45个，良性120个，不满意7个，不确定12个；经术后病理或临床随访，恶性146个，良性128个，US-FNAB细胞学结果和实际结果比较差异有统计学意义（P<0.001）。US-FNAB细胞学诊断TI-RADS 4类甲状腺结节的灵敏度、特异度、阳性预测值、阴性预测值及准确率分别为93.83%、96.09%、96.48%、93.18%和94.89%。结论 US-FNAB检查对TI-RADS 4类甲状腺结节有较高的诊断价值，能有效提高术前诊断的准确性。TI-RADS分类有助于甲状腺可疑结节临床处理方式的选择。

Objective To explore the diagnostic value of ultrasound-guided fine-needle aspiration biopsy (US-FNAB) for thyroid imaging reporting and data system (TI-RADS) 4 class thyroid nodules. Methods The preoperative ultrasound features of patients with thyroid nodule who received US-FNAB examination in Ruijin Hospital of Shanghai Jiao Tong University School of Medicine were retrospectively analyzed. The malignant risk of each nodule was evaluated and classified according to TI-RADS. A total of 281 TI-RADS 4a, TI-RADS 4b, and TI-RADS 4c class thyroid nodules of 265 patients were classified as suspicious nodules and received US-FNAB examination. The US-FNAB cytological diagnosis results, pathological results, or follow-up findings of 274 nodules were compared and studied after eliminating patients whose diagnostic results were irrelevant to cytology. Results Among 281 TI-RADS 4 class thyroid nodules diagnosed by the cytology, 97 nodules were malignant; 45 nodules were suspicious of malignancy; 120 nodules were benign; 7 nodules were unsatisfactory; and 12 nodules were undetermined. According to postoperative pathological results or clinical follow-ups, 146 nodules were malignant and 128 nodules were benign. The difference of US-FNAB cytological diagnosis results and actual results was statistically significant (P<0.001). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US-FNAB cytological diagnosis of TI-RADS 4 class thyroid nodules were 93.83%, 96.09%, 96.48%, 93.18%, and 94.89%, respectively. Conclusion US-FNAB examination is valuable for the diagnosis of TI-RADS 4 class thyroid nodules and can effectively improves the accuracy of preoperative diagnosis. TI-RADS classification is helpful for choosing clinical treatments of suspicious thyroid nodules.