The metastatic process is a very complex one. Since the seed and soil mechanism proposed by Paget as an explanation, the mechanism of metastatic colonization has showed a complexity that could not be foreseen until recently. The intervention of cytokines produced by the tumor that prepare the metastatic niche, the migration of endothelial stem cells, the modifications at niche cells and conective tissue are concepts under research. These explains why today we know that a rich blood supply may be a necessary condition but it is insufficient for the survival of a metastatic colony.