Figure 1.

Cancer stem cell hypothesis continues to evolve. (A) traditional cancer stem cell hypothesis suggested hierarchal model where only certain stem-like cell (red) retained capacity to repopulate a tumor and drive continued tumor progression, (B) the clonal model of stem cell propagation suggests many cells within the tumor retains this stem-like repopulation capacity, (C) the newest models suggest a hybrid model that allows for dedifferentiation and transdifferentiation within a tumor from multiple stem precursors in response to intra- and extratumoral pressures, driving tumor recurrence and heterogeneity