Clinical implications and perspectives of portal venous circulating tumor cells in pancreatic cancer

Figure 2 Characteristic stages of circulating tumor cells during metastasis. Cells from the primary tumor undergo epithelial-mesenchymal transition, which enables them to disseminate to blood vessels. Cancer cells travel as various phenotypes of circulating tumor cells (CTCs) and extravasate the vascular system after undergoing mesenchymal-epithelial transition. This reverse process allows CTCs to escape from blood vessels into distant organs to form a metastatic tumor. CTC: Circulating tumor cell; EMT: Epithelial-mesenchymal transition; MET: Mesenchymal-epithelial transition.