The cancer stem cell (CSC), or alternatively referred to as the tumor initiating cell (TIC) model, proposes that human cancers are organized in a hierarchical structure with the CSC at the apex. Cancer stem cells are functionally defined by their ability to self-renew, and to recapitulate the hierarchy of the original tumor from which they were derived. Emerging data from the literature suggest that CSCs might be the fraction within the tumor that resists conventional therapies; hence, the CSC paradigm provides new insight into tumor progression and relapse. Herein, we provide literature review of the CSC model, with emphasis on the translational and clinical implications of this model.