Cancer Stem Cells—Biopathology with Reference to Head and Neck Cancers

Researchers have proposed that tumor development is based exclusively on the activity of cancer stem cells (CSCs), the so-called CSC hypothesis. This new model of carcinogenesis may offer insights into the high mortality of oral cancer, the poor response to treatment, and the elevated risk of multiple tumors in patients with oral squamous cell carcinoma (OSCC). Greater knowledge is needed of the molecular pathways that participate in maintaining the stem cell (SC) state in order to understand the mechanisms involved in tumor and metastasis development. This endeavor requires the development of specific markers to identify SCs and CSCs in tissues and to determine topographic relationships with their lineage. This chapter provides an update on the literature related to stem cells and oral cancer, centering on the CSC hypothesis in this context and on progress in the identification of oral stem cells.