MET and neoplasm: These steps include: (1) detachment of cancer cells from the primary tumor and invasion through the basal lamina, (2) intravasation of cancer cells into the circulatory system, (3) survival of cancer cells within the vasculature as circulating tumour cells (CTCs), and (4) when CTCs undergo MET that enables extravasation, colonization and growth within the distant metastatic site [21,22] (Figure 2).