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.