Ultrasound classification of thyroid nodules: does size matter?

OBJECTIVE: To determine whether the size of thyroid nodules in ACR-TIRADS ultrasound categories 3 and 4 is correlated with the Bethesda cytopathology classification. METHODS: Thyroid nodules (566) subclassified as ACR-TIRADS 3 or 4 were divided into three size categories according to American Thyroid Association guidelines. The frequency of different Bethesda categories in each size range within ACR-TIRADS 3 and 4 classifications was analyzed. RESULTS: Most nodules in both ACR-TIRADS classifications fell in the Bethesda 2 category, regardless of size (90.8% and 68.6%, ACR-TIRADS 3 and 4 respectively). The prevalence of Bethesda 6 nodules in the ACR-TIRADS 4 group was 14 times higher than in the ACR-TIRADS 3 group. There were no significant differences between nodule size and fine needle aspiration biopsy classification in any of the ACR-TIRADS categories. CONCLUSION: Size does not appear to be an important criterion for indication of fine needle aspiration biopsy in thyroid nodules with a high suspicion of malignancy on ultrasound examination.