The metastatic process is a very complex phenomenon involving genetic alterations, cells and a microenvironment. In order to succeed in its metastatic implantation, the cancer cell must possess a certain number of specific properties that allow it to survive. This metastatic process is prepared from the local phase of the cancer. Indeed, during tumor growth, cancer cells undergo successive mutations linked to the genomic instability of cancers. These mutations lead to the selection of specific cell clones called metastasizing cell clones that have all the necessary capacities to successfully implant and grow as secondary tumors. During their migration, the tumor cells will have to face the host immune system to promote their dissemination. Even if the treatment of metastatic cancer is still far from being achieved, new targeted molecules offer precise actions, testifying to a more and more detailed knowledge of the mechanisms involved.