目的：分析无淋巴结转移乳头状甲状腺癌（Papillary thyroid carcinoma，PTC）的CT误诊及漏诊原因，旨在更加准确把握CT诊断PTC的价值与限度。方法：回顾性分析16例（共18个PTC病灶）经手术及病理证实的PTC病例，术前均行甲状腺CT平扫及增强检查，CT检查误诊或漏诊，观察CT平扫及增强表现，分析CT误漏诊原因。结果：16例PTC病例共18个PTC病灶（13个PTC病灶在CT上显示，5个PTC微灶未在CT上显示），9例为多发甲状腺结节（7例为结节性甲状腺肿合并PTC，2例有2个PTC微癌灶）；误诊13个，平均直径9.3 mm，7个误诊为结节性甲状腺肿，5个未定性诊断，1个误诊为腺瘤；漏诊5个PTC病灶，平均直径2.4 mm。结论：病灶多发、直径小、影像表现缺乏特异性及对典型征象缺乏认识是 PTC误诊的主要原因；5 mm以下PTC病灶在CT上难以清晰显示，可能是漏诊的主要原因。

Objective: To analyze the misdiagnosis and missed diagnosis of papillary thyroid carcinoma(PTC) without metastasis on CT, and to investigate the value and limitation of CT in diagnosis of PTC. Methods: Plain and enhanced CT scan of 16 cases of PTC(18 lesions in total) misdiagnosed or missed diagnosed proved by surgery and pathology was retrospectively analyzed. Reasons of CT misdiagnosis and missed diagnosis were analyzed. Results: There were a total of 18 PTC lesions(13 PTC lesions were shown on CT, 5 PTC micro-lesions were not shown on CT) in the 16 cases. In 9 cases, the thyroid lesion were multiple(7 cases were nodular goiter with 1 PTC lesion, while 2 cases had 2 PTC lesions). Thirteen cases were misdiagnosed, with an average diameter of 9.3 mm, among which 7 were misdiagnosed as nodular goiter, one was misdiagnosed as adenoma and five others were not definitely diagnosed. The average diameter of the 5 missed lesions was 2.4 mm. Conclusion: Multiple lesions, small diameter, lack of specific imaging character and lack of understanding of the typical signs are the main reasons of misdiagnosis of PTC. PTC lesions below 5 mm on CT are difficult to be shown, which may be the main cause of misdiagnosis.