Frequencies and malignancy rates of 6-tiered Bethesda categories of thyroid nodules according to ultrasound assessment and nodule size.

Abstract

The malignancy risk of thyroid nodules differs according to Bethesda category, ultrasound features, and nodule size. In 2725 thyroid nodules that underwent ultrasound-guided fine-needle aspiration, frequencies and malignancy rates of Bethesda categories were compared according to size and ultrasound assessment. When comparing the ultrasound suspicious nodules ≤10 mm and >10 mm, the frequency of the benign cytology was statistically higher in the >10 mm group, whereas the nondiagnostic and suspicious for malignancy cytology were higher in the ≤10 mm group. In ultrasound suspicious nodules ≤10 mm, the malignancy rate of the benign cytology group was higher but that of the suspicious for malignancy cytology group was lower than the >10 mm group. Benign and suspicious for malignant cytological results are more reliable in thyroid nodules >10 mm compared to ≤10 mm displaying suspicious ultrasound features.