title: Invasive and noninvasive thymoma: distinctive CT features.
abstract: OBJECTIVE
  The purpose of this work was to evaluate the CT features of thymoma and to determine the most helpful findings in differentiating invasive from noninvasive thymoma.
  
  
  METHODS
  The CT scans from 27 patients with invasive thymoma and 23 with noninvasive thymoma were independently assessed by two observers without knowledge of their invasiveness. The presence and distribution of various CT findings were independently analyzed.
  
  
  RESULTS
  Invasive thymomas were more likely to have lobulated (16/27, 59%) or irregular (6/27, 22%) contours than noninvasive thymomas (8/23, 35% and 1.5/23, 6%, respectively) (p < 0.05). Invasive thymomas had a higher prevalence of low attenuation areas within the tumor (16/27, 60%) than noninvasive thymomas (5/23, 22%) (p < 0.001) as well as foci of calcification (14.5/27, 54% vs. 6/23, 26%; p < 0.01).
  
  
  CONCLUSIONS
  The presence of lobulated or irregular contour, areas of low attenuation, and multifocal calcification is suggestive of invasive thymoma.
authors.affiliation: Department of Radiology, Osaka University Medical School, Japan. tomiyama@radiol.med.osaka-u.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Tomiyama
authors.forename: N L
authors.initials: NL
authors.lastname: Müller
authors.forename: S J
authors.initials: SJ
authors.lastname: Ellis
authors.forename: J R
authors.initials: JR
authors.lastname: Cleverley
authors.forename: M
authors.initials: M
authors.lastname: Okumura
authors.forename: S
authors.initials: S
authors.lastname: Miyoshi
authors.forename: M
authors.initials: M
authors.lastname: Kusumoto
authors.forename: T
authors.initials: T
authors.lastname: Johkoh
authors.forename: S
authors.initials: S
authors.lastname: Yoshida
authors.forename: N
authors.initials: N
authors.lastname: Mihara
authors.forename: O
authors.initials: O
authors.lastname: Honda
authors.forename: T
authors.initials: T
authors.lastname: Kozuka
authors.forename: S
authors.initials: S
authors.lastname: Hamada
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D000368:Aged; D002114:Calcinosis; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D009361:Neoplasm Invasiveness; D018709:Statistics, Nonparametric; D013945:Thymoma / Q000000981:diagnostic imaging* / Q000473:pathology; D013953:Thymus Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed