[Metastatic diffusion, angiogenesis and metastasogenesis]

Metastatic diffusion is the result of a progressive, well structured and organized cascade of steps. The angiogenesis, the epithelial mesenchymal transition, the premetastatic niche or the metastatic signature theory are considered as new concepts which participate in an irreversible process which escapes from the host control. The capacity to colonize one organ and not another could be explained by the "seed and soil" theory which postulates that tumor cells (the seed) will only grow in an appropriate tissue microenvironment (the soil). At the opposite, the concept of a metastatic gene expression pattern which is (or is not) expressed in the primary tumor is in opposition with the classical clonal selection hypothesis.