title: Malignancy risk stratification in thyroid nodules with nondiagnostic results at cytologic examination: combination of thyroid imaging reporting and data system and the Bethesda System.
abstract: OBJECTIVE
  To evaluate the malignancy risks of thyroid nodules with nondiagnostic results at ultrasonography (US)-guided fine-needle aspiration biopsy ( FNAB fine-needle aspiration biopsy ) and the criteria for selecting those for repeat US-guided FNAB fine-needle aspiration biopsy according to the thyroid imaging reporting and data system ( TIRADS thyroid imaging reporting and data system ).
  
  
  METHODS
  This retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. Five hundred forty-eight nondiagnostic nodules were included. US features of internal composition, echogenicity, margin, calcifications, shape, and vascularity were evaluated, and thyroid nodules were classified according to TIRADS thyroid imaging reporting and data system . TIRADS thyroid imaging reporting and data system category 3 included nodules without any suspicious features of solidity, hypoechogenicity or marked hypoechogenicity, microlobulated or irregular margins, microcalcifications, and taller-than-wide shape. Categories 4a, 4b, 4c, and 5 included nodules with one, two, three or four, or five suspicious US features. The malignancy risk was calculated.
  
  
  RESULTS
  Of the 548 nodules, 40 (7.3%) were malignant and 508 (92.7%) were benign. The malignancy risks of categories 3 and 4a nodules were 0.8% and 1.8%, respectively, whereas the malignancy risks of categories 4b, 4c, and 5 nodules were 6.1%, 14.4%, and 31%. In the 294 nodules larger than 10 mm, the malignancy risks of categories 3, 4a, 4b, 4c, and 5 nodules were 0.9%, 1.3%, 0%, 15%, and 33%, respectively. In the 254 nodules measuring 10 mm or smaller, the malignancy risks of categories 3, 4a 4b, 4c, and 5 nodules were 0%, 2.7%, 14%, 14.3%, and 31%.
  
  
  CONCLUSIONS
  Nondiagnostic thyroid nodules without suspicious US features and those with one suspicious feature can be followed up with US, but nondiagnostic nodules with two or more suspicious features should undergo repeat US-guided FNAB fine-needle aspiration biopsy.
authors.affiliation: From the Department of Radiology, Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, 50 Yonse-ro, Seodaemun-gu, 120-752 Seoul, Korea.
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Moon
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Kim
authors.forename: Jung Hyun
authors.initials: JH
authors.lastname: Yoon
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kwak
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D018276:Carcinoma, Medullary / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D002291:Carcinoma, Papillary / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D061705:Image-Guided Biopsy; D008297:Male; D008875:Middle Aged; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D013964:Thyroid Neoplasms / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D016606:Thyroid Nodule / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D047368:Tumor Burden; D014463:Ultrasonography