Re: Subdivision of intermediate suspicion, the 2021 K-TIRADS, and category III, indeterminate cytology, the 2017 TBSRTC, 2nd edition, in thyroidology: let bygones be bygones?

How to cite this article: Kim H, Hahn SY, Shin JH, Kim MK. Re: Subdivision of intermediate suspicion, the 2021 K-TIRADS, and category I I I , indeterminate cytology, the 2017 TBSRTC, 2nd edition, in thyroidology: let bygones be bygones?. Ultrasonography 2023 Sep 11 [Epub]. https://doi.org/10.14366/usg.23172 We were greatly interested to read the letter to the editor from Sengul and Sengul, which pertains to our recent paper on the subcategorization of intermediate suspicion thyroid nodules, based on suspicious ultrasonographic (US) findings [1]. We appreciate the interest that Sengul and Sengul have shown in our paper and value their insightful comments on the complex issue of subdivision. The main focus of their comment and question seems to be about the echogenicity of the included thyroid nodules. We agree that our explanation of the nodules' echogenicity may not have been sufficiently clear. However, our initial study population was restricted to thyroid nodules in the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) category 4 (intermediate suspicion) [1,2]. Therefore, from the outset, our study did not include any partially cystic or isoechoic/ hyperechoic nodules without any of the three suspicious US findings (punctate echogenic foci, nonparallel orientation, or irregular margins). These were classified as K-TIRADS category 3 (low suspicion). Similarly, we did not include solid hypoechoic nodules with any of the three suspicious US findings, as these were initially classified as K-TIRADS category 5, as Sengul and Sengul correctly noted. The K-TIRADS category 4 (intermediate suspicion) includes three types of nodules: (1) solid hypoechoic nodules without any of the three suspicious US findings, (2) entirely calcified nodules, and (3) partially cystic or isoechoic/hyperechoic nodules with any of the three suspicious US findings. Therefore, in our study, the "nodules without suspicious findings" group included solid hypoechoic nodules without any of the three suspicious US findings and entirely calcified nodules which do not allow for the assessment of nodule echogenicity. The "nodules with suspicious findings" group only included partially cystic or isoechoic/hyperechoic nodules with any of the three suspicious US findings. Consequently, the conclusions of our study remain unchanged. We agree with Sengul and Sengul regarding the importance of focusing on the subdivision of the intermediate or indeterminate category, whether from a pathological or radiological perspective. We extend our sincere gratitude to the authors for their valuable contribution to the discussion.