  The notion that there are subpopulations of cells within a tumor that play a distinctive role—either in initiating a cancer, or in seeding new cancers, has been influential in current research, suggesting new avenues for both treatment and prevention. Historically the cancer stem cell theory (CSC) was framed in opposition to the somatic mutation theory (e.g. Reya, et al. 2001; Wicha, et al. 2006; Shipitsin, et al. 2007). Laplane (2016) has argued that the cancer stem cell theory (CSC) has various advantages over the alternative, which she calls the “classical” theory. Laplane takes the following to be the four fundamental theses of CSC theory: