Metastasis is a medical term that means the development of secondary malignant growths at a distance from a primary site. It refers to a pathogenic agent's spread from the initial site to a different site within the host's body.
This term is typically used in cancers, in which it is the process by which cancer cells spread to other parts of the body. Metastatic cancer cells have features similar to the primary cancer but not like the cells in the place where the metastatic cancer is found. It is generally distinguished from cancer invasion, which is the direct extension and penetration by cancer cells into neighboring tissues.