Korean Society of Thyroid Radiology (KSThR) guidelines for the management of pediatric thyroid nodules: Suitability and risk factors

Background: The guideline for managing pediatric thyroid nodules has not been established. We investigated the appropriateness of the Korean Society of Thyroid Radiology (KSThR) guidelines and the need to consider risk factors for managing pediatric thyroid nodules. Methods: From August 2007 to February 2020, a database of thyroid nodules in patients younger than 19 years who underwent fine-needle aspiration (FNA) was analyzed. Two radiologists retrospectively reviewed ultrasound images to characterize the nodules according to the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) criteria. Thyroid nodules were divided into benign and malignant nodules. Clinical risk factors were identified, including familial thyroid cancer, history of radiation therapy, and underlying thyroiditis. According to the K-TIRADS categories and the presence of risk factors, malignancy rates were calculated. We compared the diagnostic performance of the original KSThR guidelines and newly suggested criteria for FNA derived by simulation tests with variable size cutoffs in the total study population, a group with risk factors, and a group without risk factors. Results: A total of 107 patients (mean age, 13.9 years; range, 4-18 years; 83 females; 50 patients with risk factors) with 133 nodules (71 benign and 62 malignant) were included. The malignancy rate of thyroid nodules was higher in the group with risk factors (64.0%) than in the group without risk factors (43.9%; p = 0.037). Compared with the KSThR guideline (≥1.0 cm for K-TIRADS 4 and 5), the accuracy was higher (62.4% vs. 56.4%) and the unnecessary biopsy rate was lower (44.0% vs. 47.4%) when the new criteria (≥0.6 cm for K-TIRADS 4 and ≥0.5 cm for K-TIRADS 5) were used in the total study population. In particular, in the group with risk factors, the newly suggested size criteria had a much higher accuracy (73.1% vs. 59.7%) and lower unnecessary biopsy rate (30.4% vs. 35.5%) than the KSThR guideline. Conclusions: For the management of thyroid nodules in children, it is necessary to consider risk factors and adjust the criteria values for FNA. FNA should be considered in children with risk factors for thyroid cancer even if thyroid nodules are small.