Figure 1.

Phases of metastasis. Initially, tumor cells undergo genetic mutations that enable them to detach from the primary site. Subsequently, these cells invade surrounding tissues, aided by enzymes that degrade the extracellular matrix. As they migrate, these cells may undergo epithelial to mesenchymal transition and enter blood or lymphatic vessels, as circulating tumor cells. Eventually, they exit the vessels at distant sites, adhere to new tissue, and proliferate, forming secondary tumors. This process is facilitated by interactions with the host immune system and the tumor microenvironment.