Ultrasound criteria (EU-TIRADS) to identify thyroid nodule malignancy risk in adolescents. Correlation with cyto-histological findings.

INTRODUCTION: Thyroid nodule (TN) harbouring a thyroid carcinoma are more common in paediatric than adult patients. In paediatric population, the evaluation of a TN should require specific paediatric tools for its diagnostic and therapeutic management. High-resolution ultrasonography and cytological evaluation after fine-needle aspiration biopsy (FNAB) remain the cornerstones of evaluation of TN.

OBJECTIVES: To evaluate in paediatric TN for the first time the usefulness and precision of the ultrasound criteria defined by the "Thyroid Imaging Reporting and Data System (EU-TIRADS) 2017 in adults" to establish the ultrasound indication for the practice of FNAB and stratify the risk of malignancy.

PATIENTS AND METHODS: 24 paediatric patients under age 18 years with thyroid nodules were attended in the last 15 years, 24 of them (31 nodules; age: 15.2 ± 2.2 years; 18 women) met the inclusion criteria: FNAB with Bethesda classification and ultrasound with EU-TIRADS score. EU-TIRADS score were evaluated retrospectively. Fourteen patients underwent surgery and the definitive histological diagnosis was obtained, this allowed the calculations of sensitivity, specificity and positive and negative predictive values of the EU-TIRADS and Bethesda classification. Data on the largest diameters of the nodules were collected.

RESULTS: Of the overall 31 nodules, the distribution by EU-TIRADS (T) category was: T1 (3.2%), T2: 2 (6.4%), T3: 7 (22.6%), T4: 16 (51.6%) and T5: 5 (16.1%). All malignant nodules were included in EU-TIRADS category 4 or 5. By the other hand, 13 of the 25 benign nodules were also included in the EU-TIRADS 4 category, and one in the 5. The distribution by categories of Bethesda's classification (B): BI: 6 (19.4%), BII: 14 (45.2%), BIII: 5 (16.1%), BIV: 2 (6.5%), BV: 0 and BVI: 4 (12.9%). The pathological diagnosis of the 14 patients who underwent surgery was: 6 papillary carcinomas and 8 with benign lesions: 6 nodular hyperplasia and 2 follicular adenoma. The percentage of malignancy was 42%. The sensitivity of the EU-TIRADS classification to detect malignant nodules was 100%, the specificity was 25%, PPV 44% and NPV 100%. The sensitivity of the Bethesda classification to detect malignant nodules was 86%, the specificity was 75%, PPV 67% and NPV 90%. The analysis of the largest diameter of the nodules did not show statistically significant differences between benign and malignant lesions.

CONCLUSIONS: EU-TIRADS for ultrasonographic criteria classification in combination with the clinical history is an adequate and reproducible method to estimate suspicion of malignancy of paediatric TN. It is also a reliable diagnostic tool to decide which nodules will be candidates for FNAB.