title: Value of US correlation of a thyroid nodule with initially benign cytologic results.
abstract: OBJECTIVE
  To investigate the value of ultrasonographic (US) features in thyroid nodules with initially benign cytologic results.
  
  
  METHODS
  The institutional review board approved this retrospective study and required neither patient approval nor informed consent for the review of images and records. From October 2003 to February 2006, 6118 focal thyroid nodules in 6025 consecutive patients underwent US-guided fine-needle aspiration biopsy (FNAB). This study included 1343 nodules 1 cm or larger in 1302 patients that were diagnosed as benign at initial cytologic evaluation and underwent pathologic or follow-up study. We compared the risk of malignancy according to US findings and calculated the likelihoods of different subgroups having benign nodules.
  
  
  RESULTS
  In total, 26 (1.9%) malignant and 1317 (98.1%) benign nodules were found according to reference standards. If initial cytologic results showed benign thyroid nodules, the likelihood of the nodule actually being benign was 98.1%. When a thyroid nodule had benign results at both initial and repeat FNAB, the likelihood increased to 100%. The likelihood of having a benign thyroid nodule with suspicious US features was lower (79.6%) than having a benign thyroid nodule with negative US features (99.4%, P<.001). In the nodule with benign features at initial US, the risk of malignancy for a thyroid nodule with an increase in size at follow-up US was slightly higher (1.4%) than that of a thyroid nodule with no interval change or decrease in size, but it was not significantly different (0.5%, P = .354).
  
  
  CONCLUSIONS
  Repeat FNAB should be performed for thyroid nodules that have suspicious US features, even if the initial cytologic results indicate that it is a benign lesion.
authors.affiliation: Department of Radiology, Research Institute of Radiological Science, Yonsei University College of Medicine, 134 Shinchon-Dong, Seodaemun-gu, Seoul 120-752, Korea.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kwak
authors.forename: Hyeryoung
authors.initials: H
authors.lastname: Koo
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Youk
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Kim
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Moon
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Son
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D016009:Chi-Square Distribution; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D016606:Thyroid Nodule / Q000000981:diagnostic imaging* / Q000473:pathology; D018084:Ultrasonography, Interventional