Alteration Trend and Overlap Analysis of Positive Features in Different-Sized Benign and Malignant Thyroid Nodules: Based on Chinese Thyroid Imaging Reporting and Data System.

Purpose: This study aimed to investigate the alteration trends and overlaps of positive features in benign and malignant thyroid nodules of different sizes based on the Chinese Thyroid Imaging Reporting and Data System (C-TIRADS). Patients and Methods: 1337 patients with 1558 thyroid nodules were retrospectively recruited from November 2021 to December 2023. These nodules were divided into three groups according to maximum diameter: A (≤10 mm), B (10-20 mm), and C (≥20 mm). C-TIRADS positive features were compared between benign and malignant thyroid nodules of different sizes. In addition, the trends of positive features with changes in nodule size among malignant thyroid nodules were analyzed. Results: The incidence of positive features in malignant thyroid nodules was higher than that in benign. As benign nodules grow, the incidence of all positive features showed a linear decreasing trend (Z values were 72.103, 101.081, 17.344, 33.909, and 129.304, P values < 0.001). With the size of malignant thyroid nodules increased, vertical orientation, solid, marked hypoechogenicity, and ill-defined/irregular margins/extrathyroidal extension showed a linear decreasing trend (Z = 148.854, 135.378, 8.590, and 69.239, respectively; P values < 0.05), while suspicious microcalcifications showed a linear increasing trend (Z = 34.699, P<0.001). In terms of overlapping characteristics, group A had a significantly higher overlapping rate than the other two groups, and the overlapping rate of solid indicators remained the highest among all three groups (P < 0.05). Conclusion: Differences in positive features were observed between thyroid nodules of different sizes. Except for suspicious microcalcifications, the incidence of other four positive features decreased with increasing nodule size. In addition, a negative correlation was observed between the overlap rate and nodule size. These results may provide a basis for sonographers to upgrade or downgrade thyroid nodules based on their own experience.