[Etiology, epidemiology, biology. Lung carcinogenesis]

Lung cancer is a complex disease involving various oncogenic pathways. Its early detection, at pre-invasive stages, could offer the opportunity of improving the bad prognosis of this cancer. Pre-invasive stages exist for different forms of lung cancer and some of them are recognized as being preneoplastic: dysplasias and in situ carcinoma, atypical adenomatous hyperplasia and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia are supposed to be precursors of squamous cell carcinomas, adenocarcinomas and carcinoid tumors, respectively. The sequence of histological modifications of bronchial mucosa preceding the development of a squamous cell carcinoma are well documented while those preceding other histological types are less known. This paper summarizes available data about histological modifications defining those preneoplastic and/or pre-invasive lesions, their principal clinical characteristics and the possibilities for their diagnosis. It also discusses arguments for their preneoplastic nature, their evolution and risk of progression risk, molecular abnormalities involved in lung carcinogenesis and clinical relevance of these lesions.