The cancer stem cell model. The cancer stem cell model, also known as the Hierarchical Model proposes that tumors are hierarchically organized (CSCs lying at the apex (Fig.
CSCs may generate tumors through the stem cell processes of self-renewal and differentiation into multiple cell types. Such cells are hypothesized to persist in tumors as a distinct population and cause relapse and metastasis by giving rise to new tumors.
Stationary cancer stem cells are embedded in early carcinomas and these cells are detectable in the differentiated central area of a tumor. The important step toward malignancy is the induction of epithelial mesenchymal transition (EMT) in the stationary cancer stem cells (SCS), which become mobile or migrating cancer stem cells.