Department of Radiology, Human Medical Imaging and Intervention Center, Korea
Lately, the application of US has been further emphasized for the personalized management of patients with thyroid nodules. Recently, the Korean Society of Thyroid Radiology（KSThR）has published the revised recommendations for the US diagnosis and imaging-based management of thyroid nodules（1）, and the KTA（Korean Thyroid Association）adopted the US-based malignancy risk stratification system for thyroid nodules which was proposed by KSThR（2）. The US-based malignancy risk stratification has an essential role in deciding for or against FNA of thyroid nodules and for the follow-up and post-FNA management strategies after FNA in thyroid nodules. The Korean Thyroid Imaging Reporting and Data System（K-TIRADS）, a simplified US-based risk stratification system was developed by a retrospective study（3）and validated by a prospective study（4）. In K-TIRADS, thyroid nodules are categorized as high suspicion（K-TIRADS 5）, intermediate suspicion（K-TIRADS 4）, low suspicion（K-TIRADS 3）, and benign（K-TIRADS 2）nodules based on their malignancy risks stratified by the US patterns composed of the integrated solidity, echogenicity, and suspicious US features（1）（Fig 1，Table 1）. Compared with the recently published international guidelines, the FNA criteria based on K-TIRADS has a relatively higher sensitivity and negative predictive value（94.5％and 94.2％，respectively）, but modest specificity and positive predictive value（62.4％and 36.2％，respectively）（5）. Many controversial issues exist regarding the US risk stratification of thyroid nodules and the US risk stratification system has not been standardized. Further active research on this issue may lead to the clinically feasible and standardized risk stratification system, which will be helpful for the personalized management of thyroid nodules. 【References】 1. Shin JH, Baek JH, Chung J, Ha EJ, Kim JH, Lee YH, et al., Korean Society of Thyroid R, Korean Society of Thyroid Radiology. Ultrasonography Diagnosis and Imaging-Based Management of Thyroid Nodules: Revised Korean Society of Thyroid Radiology Consensus Statement and Recommendations. Korean journal of radiology 2016;17:370-395. 2. Yi KH. The Revised 2016 Korean Thyroid Association Guidelines for Thyroid Nodules and Cancers: Differences from the 2015 American Thyroid Association Guidelines. Endocrinol Metab（Seoul）．2016;31（3）:373-378. 3. Na DG, Baek JH, Sung JY, Kim JH, Kim JK, Choi YJ, Seo H. Thyroid Imaging Reporting and Data System Risk Stratification of Thyroid Nodules: Categorization Based on Solidity and Echogenicity. Thyroid : official journal of the American Thyroid Association 2016;26:562-572. 4. Ha EJ, Moon WJ, Na DG, Lee YH, Choi N, Kim SJ, Kim JK. A Multicenter Prospective Validation Study for the Korean Thyroid Imaging Reporting and Data System in Patients with Thyroid Nodules. Korean journal of radiology. 2016;17:811-821. 5. Ha EJ, Na DG, Baek JH, Sung JY, Kim JH, Shin JH. Diagnostic Performance of US-based FNA Criteria for Thyroid Malignancy: A Comparative Study based on Six International Society Guidelines（unpublished data）. Fig. 1. Algorithm of K-TIRADS for malignancy risk stratification based on solidity and echogenicity of thyroid nodules Table 1. Malignancy Risk Stratification According to Korean Thyroid Imaging Reporting and Data System（K-TIRADS）and FNA Indications.