title: The prevalence and significance of incidental thyroid nodules identified on computed tomography.
abstract: OBJECTIVE
  The purpose of this study was to assess the prevalence of incidental thyroid nodules (ITN) found on computed tomography (CT) of the neck and to determine whether CT characteristics could distinguish malignant from benign thyroid lesions.
  
  
  METHODS
  We retrospectively reviewed CT scans in 734 patients without known thyroid disease (384 men and 350 women; mean age, 49.8 +/- 13.7 years). The CT findings of ITN such as size, shape (anteroposterior-transverse diameter ratio [AP/T ratio]), margin, peripheral enhancing rim, intralesional calcification, and attenuation characteristics were analyzed and correlated with ultrasonographic (US) findings.
  
  
  RESULTS
  One hundred sixty ITNs were noted in 123 (16.8%) patients. Of 120 ITNs whose histological diagnoses were available, 15 (12.5%) were malignant. Malignant nodules more frequently showed nodular or rim calcifications (46.7% vs 13.3%; P < 0.0005), AP/T ratio of greater than 1.0 (33.3% vs 9.5%; P < 0.05), and mean attenuation value on contrast-enhanced scan of greater than 130 Hounsfield units (86.7% vs 49.5%; P < 0.05) than benign nodules.
  
  
  CONCLUSIONS
  We found at least a 9.4% (15/160) prevalence of malignancy among ITN detected on CT. The further evaluation with US or biopsy should be performed, if an ITN shows CT features suggesting malignancy (calcification; AP/T ratio, >1.0; or mean attenuation value, >130 HU).
authors.affiliation: Department of Radiology, Kangdong Seong-Sim Hospital, Hallym University College of Medicine, Seoul, Republic of Korea. evee0914@chollian.net
authors.forename: Dae Young
authors.initials: DY
authors.lastname: Yoon
authors.forename: Suk Ki
authors.initials: SK
authors.lastname: Chang
authors.forename: Chul Soon
authors.initials: CS
authors.lastname: Choi
authors.forename: Eun Joo
authors.initials: EJ
authors.lastname: Yun
authors.forename: Young Lan
authors.initials: YL
authors.lastname: Seo
authors.forename: Eun Suk
authors.initials: ES
authors.lastname: Nam
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Cho
authors.forename: Young-Soo
authors.initials: YS
authors.lastname: Rho
authors.forename: Hwoe Young
authors.initials: HY
authors.lastname: Ahn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011859:Radiography; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000453:epidemiology; D016606:Thyroid Nodule / Q000000981:diagnostic imaging* / Q000453:epidemiology; D014463:Ultrasonography