分析未成年人甲状腺结节超声表现特点，探讨甲状腺细针穿刺活检（FNAB）在未成年人甲状腺结节中的应用。

回顾性选取2011年1月至2020年12月在上海交通大学医学院附属瑞金医院超声科行FNAB的408例甲状腺结节患者（共434个结节），其中未成年人组（≤18岁）204例患者和成年人组（＞18岁）204例患者，每组各217个结节。采用非参数检验（Mann-Whitney U检验）及χ²检验评估2组甲状腺结节的超声图像特征、中国超声甲状腺影像报告和数据系统（C-TIRADS）分类恶性率、淋巴结转移情况，采用敏感度、特异度、准确性评估FNAB的诊断效能。

与成年患者比较，未成年甲状腺癌患者的结节最大径较大［16.0（8.5，23.3）mm vs 8.4（5.9，12.4）mm］，垂直位及极低回声率较低（32.6% vs 58.7%；1.1% vs 7.6%），差异均具有统计学意义（U=2824.5，P＜0.001；χ²=12.806，P＜0.001；χ²=4.906，P=0.027）；未成年患者的3类、4A类、4B类、4C类甲状腺结节的恶性率（0、4.8%、33.9%、84.9%）与C-TIRADS恶性率相符，4C类结节的恶性率高于成年患者（84.9% vs 72.1%），差异有统计学意义（χ²=4.457，P=0.035）；未成年甲状腺癌患者的淋巴结转移率高达78.4%，高于成年人甲状腺癌淋巴结转移率（17.8%），差异有统计学意义（χ²=34.307，P＜0.001），2组间转移至中央区、颈侧区的转移率比较，差异无统计学意义（P＞0.05）；未成年及成年患者的甲状腺结节穿刺的诊断准确性比较（95.5% vs 96.6%），差异无统计学意义（P＞0.05），但前者诊断的假阴性率较高（5.4% vs 2.2%）。

与成年人相比，未成年人甲状腺癌结节较大，垂直位生长及极低回声较少；未成年人甲状腺结节适用于C-TIRADS风险分层；未成年人甲状腺癌的淋巴结转移率较高；未成年人患者穿刺假阴性较多，对于伴有可疑淋巴结的风险分层高的患者（4C及以上），可仅穿刺淋巴结。

To analyze the ultrasonic manifestations of thyroid carcinoma in juveniles and to discuss the application of thyroid fine needle aspiration biopsy (FNAB) in such patients.

A total of 434 nodules of 408 patients who had undergone FNAB from January 2011 to December 2020 at the Department of Ultrasound, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University were selected and divided into either a juvenile group (≤18 years old, n=204) or an adult group (＞18 years old, n=204), with 217 nodules in each group. The non-parametric test (Mann-Whitney U test) and χ² test were used to evaluate the ultrasonic image characteristics of thyroid nodules, the classification of China ultrasonic thyroid imaging reporting and data system (C-TIRADS), and lymph node metastasis in the two groups. The sensitivity, specificity, and accuracy were calculated to evaluate the diagnostic efficiency of FNAB.

Compared with those in adult patients, thyroid cancer in juveniles had significantly larger nodule maximum diameters [16.0 (8.5, 23.3) mm vs 8.4 (5.9, 12.4) mm, U=2824.5, P＜0.001], smaller probabilities of vertical position (32.6% vs 58.7%, χ²=12.806, P＜0.001), and extremely low echo (1.1% vs 7.6%, χ²=4.906, P=0.027). For juvenile patients, the rates of malignant thyroid nodules of categories 3, 4A, 4B, and 4C (0, 4.8%, 33.9%, and 84.9%, respectively) were consistent with those of C-TIRADS, and the rate of malignant nodule of category 4C (84.9%) was significantly higher than that of adult patients (72.1%; χ²=4.457, P=0.035). The lymph node metastasis probability in juveniles was as high as 78.4%, which was significantly higher than that in adult patients (17.8%; χ²=34.307, P＜0.001). There was no significant difference in the probability of metastasis to the central region and lateral cervical region between the two groups (P＞0.05). The diagnostic accuracy of thyroid nodule puncture was similar in juvenile and adult patients (95.5% vs 96.6%), but the false-negative rate in the former was higher (5.4% vs 2.2%).

Compared with thyroid cancer in adults, thyroid cancer in juveniles has larger nodules, less vertical growth, and very low echogenicity. Thyroid nodules in juveniles are eligible for the C-TIRADS risk stratification. The lymph node metastasis rate of thyroid carcinoma in juveniles is higher, and the false-negative rate of puncture for thyroid carcinoma in juveniles is also higher. For patients at high risk (4C and above) for suspicious lymph nodes, a lymph node puncture is enough.