Background: Thyroid nodules have wide ranges of estimated risks of malignancy in each cytology categories. Combined with the cytology results, ultrasonography (US) patterns can help to determine how to manage thyroid nodules. We compared efficacy of Korean Thyroid Imaging Reporting and Data System (K-TIRADS) and American College of Radiology (ACR)-TIRADS in terms of predicting risk of malignancy in each cytology categories.
Methods: Among 1153 thyroid fine needle aspiration (FNA) cases performed at Seoul National University Hospital in 2017, ultrasonography images of 225 thyroid nodules, which have been pathologically confirmed by core needle biopsy or surgery, were reviewed by two medical doctors. Binominal test was used to investigate interaction between FNA cytology and US pattern (K-TIRADS and ACR-TIRADS) in assessment of the malignancy risk of thyroid nodules.
Results: Among 225 finally diagnosed thyroid nodules, 119 nodules (52.9%) were confirmed as malignancy. Overall, malignancy risks were 20.3%, 28.5%, 75.0%, 98.5% in thyroid nodules of Bethesda category III, IV, V, VI, respectively. Among 119 malignancy nodules, proportion of each categories were similar between K-TIRADS and ACR-TIRADS (Category III, 3.4% vs 3.4%; category IV, 15.1% vs 16.0%; category V, 81.5% vs 80.5%). In benign and suspicious for malignancy nodules, low suspicious US pattern in K-TIRADS significantly decreased the malignancy risk, whereas low suspicious US pattern in ACR-TIRADS did not change the risk of malignancy. Both high suspicious US pattern in K-TIRADS and ACR-TIRADS significantly increased the risk of malignancy in benign, atypia of undetermined significance/follicular lesion of undetermined significance, and suspicious for malignancy nodules.
Conclusion: The malignancy risk of thyroid nodules can be more effectively evaluated using combined cytology results and sonographic patterns. K-TIRADS may be more useful to assess malignancy risk in Bethesda category II, V nodules compared to ACR-TIRADS.