title: Does the World Health Organization histological classification predict outcomes after thymomectomy? Results of a multicentre study on 750 patients.
abstract: OBJECTIVE
  The World Health Organization (WHO) thymoma histological classification clinical value remains a controversy. In this study, we evaluated its prognostic significance in patients with thymoma treated with radical intent.
  
  
  METHODS
  Six high-volume Italian Thoracic Surgery Institutions collaborated with their own retrospective anonymized datasets. Demographic, clinical, pathological and treatment data were examined. A WHO histological classification (WHO-HC) collapsed scheme (A/AB and B1/B2 types merged) was proposed and compared with the traditional one. Predictors of survival were assessed using a Cox model with shared frailty. Competing-risk regression models were performed to identify the association between individual factors and freedom from recurrence.
  
  
  RESULTS
  Between 1990 and 2011, 750 thymomas were operated on in participating centres. Myasthenia gravis was observed in 363 (48%) patients. A complete resection was achieved in 676 (91%) cases. One hundred and nine patients (15%) had a WHO-HC A type, 166 (22%) AB, 179 (24%) B1, 158 (21%) B2 and 135 (18%) B3. The rate of 5-year OS and cumulative incidence of recurrence for all cases was 91% and 0.11, respectively. Five-year survival rates by WHO-HC in the collapsed scheme were A/AB 93%, early-B 90% and advanced-B 85%. Masaoka stage only was demonstrated to be an independent predictor for survival and recurrence. The WHO-collapsed scheme showed a trend in influencing recurrence overall survival development (hazard ratio: 1.32; P = 0.16).
  
  
  CONCLUSIONS
  Our results show evidence of lack of significance by WHO-HC in influencing prognosis, even though the proposed collapsed scheme revealed a fair stratification of risk to relapses and better correlation with patients' clinical characteristics.
authors.affiliation: Department of Thoracic Surgery, University of Torino, Torino, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Guerrera
authors.affiliation: Sapienza University of Rome, Fondazione Eleonora Lorillard Spencer Cenci, S. Andrea Hospital, Rome, Italy.
authors.forename: Erino Angelo
authors.initials: EA
authors.lastname: Rendina
authors.affiliation: Sapienza University of Rome, Fondazione Eleonora Lorillard Spencer Cenci, Policlinico "Umberto I", Rome, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Venuta
authors.affiliation: Catholic University 'Sacred Heart' Rome, Rome, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Margaritora
authors.affiliation: Sapienza University of Rome, Fondazione Eleonora Lorillard Spencer Cenci, S. Andrea Hospital, Rome, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Ciccone
authors.affiliation: Catholic University 'Sacred Heart' Rome, Rome, Italy.
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Novellis
authors.affiliation: San Giovanni Battista Hospital, Service of Pathology, Torino, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Novero
authors.affiliation: Sapienza University of Rome, Fondazione Eleonora Lorillard Spencer Cenci, Policlinico "Umberto I", Rome, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Anile
authors.affiliation: Department of Thoracic Surgery, University of Torino, Torino, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Bora
authors.affiliation: 'Amedeo Avogadro' University Novara, Italy Unit of Thoracic Surgery, Novara, Italy.
authors.forename: Ottavio
authors.initials: O
authors.lastname: Rena
authors.affiliation: University of Pisa, Pisa, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Casadio
authors.affiliation: University of Pisa, Pisa, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Mussi
authors.affiliation: Unit of Cancer Epidemiology and CPO Piedmont, San Giovanni Battista Hospital, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Evangelista
authors.affiliation: Department of Thoracic Surgery, University of Torino, Torino, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Ruffini
authors.affiliation: University of Pisa, Pisa, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Lucchi
authors.affiliation: Department of Thoracic Surgery, University of Torino, Torino, Italy pierluigi.filosso@unito.it.
authors.forename: Pier Luigi
authors.initials: PL
authors.lastname: Filosso
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000473:pathology / Q000601:surgery; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D016019:Survival Analysis; D013934:Thymectomy / Q000401:mortality; D013945:Thymoma / Q000145:classification* / Q000175:diagnosis / Q000401:mortality / Q000473:pathology / Q000601:surgery; D013950:Thymus Gland / Q000473:pathology*; D013953:Thymus Neoplasms / Q000145:classification* / Q000175:diagnosis / Q000401:mortality / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome; D014944:World Health Organization
keywords: Histology; Recurrence; Surgery; Survival; Thymoma; WHO classification