Aims: The third edition of the World Health Organization (WHO) classification of lung tumours has been published and is expected to become the standard nomenclature. The aim of this study was to assess the usability and prognostic significance of the WHO classification in comparison with other recent classifications.
Methods and results: One hundred and forty-seven resected pulmonary adenocarcinoma cases were reviewed and histologically classified according to the WHO classification (1999) and the classification by Noguchi (1995). Papillary carcinomas as described by Silver and Askin (1997) were also identified. Since the papillary type in the WHO classification is not strictly defined, we compared the following two kinds of WHO classification: (i) WHO-N; WHO classification adopting Noguchi Type F as the definition of the papillary type, namely, pure papillary adenocarcinoma without a bronchioloalveolar component; (ii) WHO-SA; WHO classification adopting papillary carcinoma by Silver and Askin as the definition of the papillary type, namely, tumour with papillary structure constituting at least 75% of the lesion. The bronchioloalveolar carcinoma of the WHO classification showed a better prognosis than other subtypes in both overall and Stage I disease limited survival analysis. In analysis limited to Stage III disease, only the papillary type of WHO-SA showed a significantly worse prognosis.
Conclusions: WHO-SA is recommended for prognostic correlation.