title: Ultrasound-Based Risk Stratification for Malignancy in Thyroid Nodules: A Four-Tier Categorization System.
abstract: OBJECTIVE
  The purpose of this study was to stratify the malignancy risk of US features, with an emphasis on nodule echogenicity.
  
  
  METHODS
  A total of 1,058 nodules of 824 consecutive patients (236 malignant and 822 benign) were included in this study. Malignancy risk of each nodule was analyzed according to US features, with an emphasis on nodule echogenecity, and was stratified into 4-tier categories.
  
  
  RESULTS
  In multivariate analysis, isoechogenicity, indistinct margin, non-solid internal content, and parallel orientation were predictive of benign nodules (P < 0.002), while hypoechogenicity, marked hypoechogenicity, spiculated/microlobulated margin, solid content, nonparallel orientation (taller than wide), microcalcification, and macrocalcification were predictive of malignancy (P ≤ 0.037). Although the presence of US features associated with malignancy was significantly predictive of malignancy in hypoechoic and markedly hypoechoic nodules (P ≤ 0.004), it was not associated with malignancy in isoechoic or hyperechoic nodules. Thyroid nodules could be stratified into four categories according to the malignancy risk: benign (risk 0%), probably benign (risk ≤ 5%), indeterminate (risk > 5 and < 50%), and suspicion of malignancy (risk > 50%).
  
  
  CONCLUSIONS
  The US-based four-tier categorization system will be useful for predicting the risk of malignancy and decisions regarding FNA for thyroid nodules.
  
  
  CONCLUSIONS
  • No US feature was predictive of malignancy in isoechoic nodules. • Isoechoic nodules without calcification can be included in the probably benign category. • We suggest a four-tier categorization stratified primarily by nodule echogenecity. • The four-tier categorization of thyroid nodules will be useful for FNA decisions.
authors: Department of Radiology, Gangnam Center, Seoul National University Hospital Healthcare System, 39F Gangnam Finance Center, 737 Yeoksam dong, Gangnam Gu, Seoul, Korea, 135-984.
authors: Hyobin
authors: H
authors: Seo
authors: Dong Gyu
authors: DG
authors: Na
authors: Ji-Hoon
authors: JH
authors: Kim
authors: Kyung Won
authors: KW
authors: Kim
authors: Ji Won
authors: JW
authors: Yoon
mesh_terms: D001707:Biopsy, Needle / Q000379:methods; D002114:Calcinosis / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D061705:Image-Guided Biopsy / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods; D016606:Thyroid Nodule / Q000000981:diagnostic imaging / Q000473:pathology*; D018084:Ultrasonography, Interventional / Q000379:methods