title: Extrathyroid extension of well-differentiated papillary thyroid microcarcinoma on US.
abstract: BACKGROUND
  Extrathyroidal extension is an important factor to determine the extent of thyroid surgery. The aim of the present study was to evaluate the usefulness of high-resolution ultrasound (US) for predicting the extrathyroidal extension of papillary thyroid microcarcinoma (PTMC).
  
  
  METHODS
  This study included a total of 221 PTMCs in 181 patients. PTMC was defined as thyroid papillary carcinoma equal or less than 1 cm in size. The US findings, such as contact and disruption of thyroid capsule, were evaluated to predict the extrathyroidal extension of thyroid carcinoma. We calculated the diagnostic accuracy and odds ratio for each US finding.
  
  
  RESULTS
  Of the 221 PTMCs, extrathyroidal extension was present in 89 (40.3%) based on pathologic results. The mean size was not significantly different between PTMCs with and without extrathyroidal extension (p = 0.527). When the degree of contact was high, extrathyroidal extension of the thyroid cancer was high (p < 0.0001). Considering the odds ratio, Az value, and positive predictive value of each US finding, more than 25% contact with the adjacent capsule is the most accurate measurement for predicting extrathyroidal extension.
  
  
  CONCLUSIONS
  This study suggests that the presence and degree of contact between a PTMC and the adjacent capsule as found on preoperative US can provide an useful predictive information about an extrathyroidal extension.
authors.affiliation: Department of Diagnostic Radiology, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kwak
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Kim
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Youk
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Kim
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Son
authors.forename: Seon Hyeong
authors.initials: SH
authors.lastname: Choi
authors.forename: Ki Keun
authors.initials: KK
authors.lastname: Oh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000473:pathology; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology; D014463:Ultrasonography