title: Using the World Health Organization Classification of thymic epithelial neoplasms to describe CT findings.
abstract: OBJECTIVE
  Our purpose was to assess the CT features of various subtypes of thymic epithelial neoplasms on the basis of the 1999 World Health Organization classification.
  
  
  METHODS
  Thymic epithelial neoplasms in 53 patients who underwent thymectomy were retrospectively assessed histologically according to the 1999 World Health Organization classification. Type A and B neoplasms correspond to thymomas and type C, to thymic carcinoma. The study included four patients with type A, 14 with type AB, nine with type B1, 14 with type B2, four with type B3, and eight with type C epithelial tumors. Two observers independently assessed the CT scans without knowledge of the histologic findings.
  
  
  RESULTS
  Type A tumors were more likely to have smooth contours on CT (4/4, 100%) and round shapes (3.5/4, 88%) than any other type of thymic epithelial tumor (all, p < 0.05). Type C tumors had a higher prevalence of irregular contours (6/8, 75%) than any other type of thymic epithelial tumor (all, p < 0.05). Calcification was more frequently seen in type B1 (4/9, 44%), type B2 (8.5/14, 61%), and type B3 (3/4, 75%) tumors than in type AB (2/14, 14%) and type C (0.5/8, 6%) tumors (all, p < 0.05).
  
  
  CONCLUSIONS
  Smooth contours and a round shape are most suggestive of type A thymic epithelial tumor, whereas irregular contours are most suggestive of type C tumor. Calcification is suggestive of type B tumors. CT is of limited value, however, in differentiating type AB, B1, B2, and B3 tumors.
authors.affiliation: Department of Radiology, Ehime National Hospital, 366, Yokogawara, Shigenobu, Ehime 791-0281, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Tomiyama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Johkoh
authors.forename: Naoki
authors.initials: N
authors.lastname: Mihara
authors.forename: Osamu
authors.initials: O
authors.lastname: Honda
authors.forename: Takenori
authors.initials: T
authors.lastname: Kozuka
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Koyama
authors.forename: Seiki
authors.initials: S
authors.lastname: Hamada
authors.forename: Meinoshin
authors.initials: M
authors.lastname: Okumura
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Ohta
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Eimoto
authors.forename: Masao
authors.initials: M
authors.lastname: Miyagawa
authors.forename: Nestor L
authors.initials: NL
authors.lastname: Müller
authors.forename: Junpei
authors.initials: J
authors.lastname: Ikezoe
authors.forename: Hironobu
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D000368:Aged; D002114:Calcinosis / Q000000981:diagnostic imaging / Q000473:pathology; D002277:Carcinoma / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009375:Neoplasms, Glandular and Epithelial / Q000145:classification* / Q000000981:diagnostic imaging / Q000473:pathology; D012189:Retrospective Studies; D013945:Thymoma / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology; D013953:Thymus Neoplasms / Q000145:classification* / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed; D014944:World Health Organization