[Biological perspectives]

The tumour biology of non-small cell bronchial cancer integrates recent developments and a dynamic schema of the phenomena of tumour progression and diffusion of the metastatic disease. There is no leap of known biological disruption between Stage II and Stage III. The latter is defined by anatomical criteria and is a transition in the continuum of the natural history of these cancers. The moto for the tumour progression is the genotypic instability and phenotypic diversification. Metastatic microscopic disease constitutes the first cause of failure in the treatment of Stage III non-small cell bronchial cancer. Among prognostic factors for survival emphasis is placed on the alterations of p53 expression, different types of aneuploidy, anomalies of the expression of cellular adhesion molecules and finally, tumour diversification towards a metastatic phenotype.