title: Prognostic and clinical relevance of the World Health Organization schema for the classification of thymic epithelial tumors: a clinicopathologic study of 108 patients and literature review.
abstract: OBJECTIVE
  Controversy has ensued about the prognostic relevance of the new World Health Organization (WHO) schema for the classification of thymoma. In this study, we present the clinical and histologic features of 108 thymomas and evaluate the usefulness of this histologic schema in view of the prognosis.
  
  
  METHODS
  Retrospective, clinicopathologic analysis of our experience and a review of recent literature.
  
  
  METHODS
  Department of Thoracic and Cardiovascular Surgery of a university hospital.
  
  
  METHODS
  A series of 108 thymomas were reviewed and classified by the new WHO schema. The clinical characteristics and the survival outcome were investigated in reference to the WHO subtypes. The Cox proportional hazards model was applied to determine the factors affecting the tumor-related survival. Recent literature on the prognostic relevance of the WHO schema was reviewed.
  
  
  RESULTS
  There were 7 type A tumors, 25 type AB tumors, 12 type B1 tumors, 32 type B2 tumors, 20 type B3 tumors, and 12 type C tumors. The histologic subtype closely correlated with the Masaoka stage (p = 0.00). The tumor-related survivals at 5 years and 10 years were 88.0% and 77.9%, respectively. Stage III and IV tumors had a significantly worse prognosis than stage I or II tumors (p < 0.05). Type B3 tumors had an intermediate prognostic ranking in comparison with the carcinomas and with the other groups. On multivariate analysis, the WHO subtype (A-B2 vs B3 vs C) could predict the tumor-related survival, but the Masaoka stage was the most important prognostic factor affecting the postoperative survival (p = 0.026).
  
  
  CONCLUSIONS
  The Masaoka stage is the most important determinant of survival in surgically resected cases of thymoma. To clarify the prognostic relevance and clinical usefulness of the WHO schema, consistent parameters reflecting the surgical outcome and development of the diagnostic tools that could improve the interobserver agreement within type B are needed.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Yonsei University College of Medicine, CPO Box 8044, Seoul, South Korea.
authors.forename: Dae Joon
authors.initials: DJ
authors.lastname: Kim
authors.forename: Woo Ick
authors.initials: WI
authors.lastname: Yang
authors.forename: Sung Sil
authors.initials: SS
authors.lastname: Choi
authors.forename: Kil Dong
authors.initials: KD
authors.lastname: Kim
authors.forename: Kyung Young
authors.initials: KY
authors.lastname: Chung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D015996:Survival Rate; D013945:Thymoma / Q000145:classification* / Q000401:mortality / Q000473:pathology; D013953:Thymus Neoplasms / Q000145:classification* / Q000401:mortality / Q000473:pathology; D014944:World Health Organization