The movement of continuous sheets of epithelial cells occurs during embryonic development, tissue repair, and cancer. Common to cellular and molecular principles of collective cell migration, invading cancers seem to reactivate embryonic pathways and patterns of cell movement. Epithelial cells possess the capability to become mesenchymal cells in a process called epithelial mesenchymal transition (EMT), which has been extensively studied and described. The aim of this article is to summarize the most recent literature data concerning less known epithelial-endothelial transition and endothelial-mesenchymal transition.