Endocrine Abstracts

Objective: To determine whether the Korean-Thyroid Imaging Reporting and Data System (K-TIRADS) 4 nodules can be subcategorized by ultrasonography (US)-based stratification of malignancy risk, and to evaluate the diagnostic performance of the modified biopsy criterion based on the subcategorization of the K-TIRADS 4 category in a multicenter cohort.

Materials and Methods: A total of 1,541 K-TIRADS 4 nodules (≥ 1 cm) with final diagnoses were included in the study. The association of US features with malignancy was assessed in the overall K-TIRADS 4 nodules and each subgroup nodule. The US criteria for subcategorization of the K-TIRADS 4 nodules were developed based on the US features, which significantly increased the malignancy risk among the K-TIRADS 4 nodules. The diagnostic performance of biopsy criterion 1 (size cut-off of 1 cm), biopsy criterion 2 (size cut-off of 1.5 cm), and modified biopsy criterion 3 (size cut-off of 1 cm for K-TIRADS 4B and 1.5 cm for K-TIRADS 4A) were evaluated in the K-TIRADS 4 nodules.

Results: US features of marked hypoechogenicity, macrocalcification, and the presence of two or three suspicious US feature significantly increased the malignancy risk of the K-TIRADS 4 nodules. The K-TIRADS 4 nodules could be subcategorized as K-TIRADS 4 B (higher risk) and K-TIRADS 4A (lower risk) according to the US criteria. The modified biopsy criterion based on the subcategorization of K-TIRADS 4 nodules reduced the unnecessary biopsy rate for malignancy by 22.5% compared with criterion 1 (P< 0.001) and increased the sensitivity by 29.6% compared with criterion 2 (P< 0.001).

Conclusion: The K-TIRADS 4 nodules were subcategorized as K-TIRADS 4B (higher risk) and K-TIRADS 4A (lower risk) based on US features and increasing malignancy risk. Modified biopsy criterion 3 can be complementarily used for biopsy criterion 2 in patients who require higher diagnostic sensitivity for malignancy.