目的：比较低危甲状腺微小乳头状癌（papillary thyroid microcarcinoma，PTMC）术前超声与术后病理测量的直径差异，并分析其与术后淋巴结转移的关系。方法：回顾性分析2021年4月至2022年1月在南京中医药大学附属中西医结合医院甲状腺乳腺外科就诊接受甲状腺腺叶切除术或全甲状腺切除术的单灶cN0M0 PTMC病人234例，比较超声与病理测量的直径差异，并分析出现颈部中央区淋巴结转移相关的风险因素。结果：PTMC中位最大直径的超声测量结果为6.8 (5.6, 8.4) mm，明显大于病理测量结果5.0 (4.0, 7.0) mm（P=0.000）。其中，37.2%的PTMC超声与病理测量直径一致，61.1%超声评估大于病理，仅1.7%超声评估小于病理。超声与病理测量的直径之间存在线性相关，回归方程可表示如下：病理直径=0.799×超声直径-0.221。28.6%的PTMC病人存在中央区淋巴结转移。多元Logistic回归分析结果表明，病理测量直径是发生中央区淋巴结转移的危险因素（OR=17.845，95%CI：2.507~127.025，P=0.004），截断值为5.5 mm，对应的超声测量直径为7.2 mm。结论：超声与病理测量单灶cN0M0 PTMC直径差异有统计学意义，但也存在显著相关性。病理直径>5.5 mm、超声测量直径>7.2 mm，PTMC发生中央区淋巴结转移的风险增加。

Objective To compare the size discrepancy between ultrasonic and pathological measurement of solitary cN0M0 papillary thyroid microcarcinoma (PTMC), and to explore their correlation with lymph node metastasis. Methods From April 2021 to January 2022, 234 patients with solitary cN0M0 PTMC who received thyroid lobectomy or total thyroidectomy in the Department of Thyroid and Breast Surgery of Nanjing University of Chinese Medicine, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine were analyzed retrospectively. The size discrepancy between ultrasonic and pathological measurement were compared, and the risk factors of central lymph node metastasis were analyzed. Results The mean of maximum diameter of PTMC measured by ultrasound was 6.8 (range 5.6 to 8.4) mm, which was significantly bigger than that measured by pathology 5.0 (range 4.0 to 7.0) mm (P=0.000). Of them, 37.2% of the tumor size measured by ultrasound is consistent with pathology, 61.1% of the tumor size measured by ultrasound is bigger than that measured by pathology, and only 1.7% of the tumor size measured by ultrasound is smaller than that measured by pathology. There was a linear correlation between the diameter measured by ultrasound and pathology. And the regression equation can be expressed as: pathological diameter =0.799 × ultrasonic diameter -0.221. In addition, 28.6% patients had central lymph node metastasis. Multivariate Logistic regression analysis showed that the diameter measured by pathology is a risk factor for central lymph node metastasis in patients (OR=17.845, 95%CI: 2.507-127.025, P=0.004), and the cutoff value is 5.5 mm which corresponded to the diameter measured by ultrasound as 7.2 mm. Conclusions The sizes of solitary cN0M0 PTMC measured by ultrasound and pathology are different but also correlated. PMTC with pathological diameter >5.5 mm with its corresponding ultrasonic diameter as 7.2 mm indicated an increased risk of central lymph node metastasis.