With the aging population and an increased incidence of neoplastic diseases, the study of the etiology of tumors and the mechanisms involved in the process of metastasis has increased significantly. Although there has been remarkable progress in this area and many proposed theories, several questions still remain. The factors associated with the emergence of the primary tumor and the mechanisms of metastasis are difficult to understand for many surgeons and clinicians because of the involvement of complex genetic, biochemical and molecular models. The tumor metastasis is responsible for approximately 90% of all cancer-related deaths. The cancer metastatic process occurs in a series of progressive steps, which called “metastatic cascade”. Its occurrence is a necessary break of the normal homeostatic mechanisms, leading to a rearrangement of the stromal tissue adjacent to the primary tumor. It is now well established that for this process, cancer cells need to acquire additional properties, which confer the capacity to invade the extracellular matrix, migrate, invade blood and lymph vessels, adhere, survive in target organs, grow and promote “organogenesis” in this new environment. The aim of this study, therefore, is to provide a didactic review and accessible information on ways and mechanisms involved in the genesis of the primary tumor and metastasis process, which may contribute to treatment of these tumors.