We have read with great respect the research article titled "Subcategorization of intermediate suspicion thyroid nodules based on suspicious ultrasonographic findings." This high-quality research appears to necessitate the subcategorization of category 4 (intermediate suspicion) according to the 2021 Korean Thyroid Imaging Reporting and Data System (K-TIRADS), based on suspicious ultrasound (US) findings [5,6]. We believe that Kim et al.'s [5] emphasis on the subdivision of "intermediate suspicion" is a significant and vital issue in the field of thyroidology, as published in Volume 42 of Ultrasonography.

We also note that it is essential for professionals such as endocrine surgeons, endocrine pathologists, endocrinologists, radiologists, head and neck surgeons, otorhinolaryngologists, and thyroidologists to stay updated on the expanding range of clinical presentations for the atypia of undetermined significance or follicular lesion of undetermined significance ("AUS/FLUS"), also known as category III of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), second edition. This knowledge is crucial to ensure appropriate clinical care and the effective use of fine-needle aspiration cytology, thereby minimizing the risk of overlooking thyroid malignancy.

We have proposed and recommended a subdivision concept for category III, TBSRTC: (1) category IIIA: AUS/FLUS without nuclear atypia (AUS/FLUS w/o NA) and (2) category IIIB: AUS/FLUS with nuclear atypia (AUS/FLUS w/NA) [7-10]. However, Kim et al. [5] stated that they focused on category 4 (intermediate suspicion) in the 2021 K-TIRADS and divided it into two subgroups: nodules without suspicious sonographic findings and nodules with suspicious findings.

It should be noted that K-TIRADS 4 includes three main sonographic groups: (1) solid hypoechoic nodules without any of the three suspicious US features (i.e., punctate echogenic foci, nonparallel orientation, or irregular margins), (2) entirely calcified nodules, and (3) partially cystic or isoechoic/hyperechoic nodules with any of the three aforementioned suspicious US features [6]. The authors have stated that they divided these groups based on suspicious US features. However, it remains unclear which types of echogenicity were used by the authors to divide the nodules in terms of suspicious US features.

It is important to clarify that while partially cystic or isoechoic/hyperechoic nodules (K-TIRADS 3) with any of the three suspicious US features are classified as K-TIRADS 4, solid hypoechoic nodules without any of the three suspicious US features (K-TIRADS 4) with any of the three suspicious US features are classified as K-TIRADS 5. Therefore, if the first group (with suspicious features) was considered, this study group would no longer be classified as K-TIRADS 4, but rather as high suspicion (K-TIRADS 5). Similarly, if the second group (without suspicious features) was considered, that study group would no longer be classified as K-TIRADS 4, but rather as low suspicion (K-TIRADS 3). Would the results of this valuable study not change if all these possibilities were considered separately in detail? Is it not essential—even crucial—in the field of thyroidology to clarify all the aforementioned categories with these mentioned conditions in each step of the discussion?

In conclusion, the debate continues regarding both intermediate (sonographic) suspicion and indeterminate thyroid nodules. To address these issues, thyroidologists may opt to work with subdivisions in the future, rather than insisting on a monolithic intermediate or indeterminate category. This approach could shed light on the subject. The saying "let bygones be bygones" may not apply here, as this issue certainly warrants further investigation. We thank Kim et al. [5] for their significant study.