GEOGRAPHICAL AND TEMPORAL

Over recent decades there have been both geographical and temporal changes in the distribution of histological subtypes of lung cancer. Knowledge of these modifica-tions may help to recognize the potential aetiologic and pathogenic mechanisms in lung cancer. Adenocarcinoma has become the leading lung cancer subtype in North America compared with Europe where the squamous cell carcinoma remains the most frequent subtype.1,2 This increase may be partly artefactual and involve several biases which are addressed in this paper. This article, based on a computerized (Medline 1966– 1996) and a manual search, reviews the epidemiology of adenocarcinoma of the lung and examines possible reasons for the differences in incidence worldwide