**1. Introduction**

Gastric cancer is the third leading cause of cancer-related deaths and the fifth most frequent cancer worldwide. The cancer in its nonmetastatic form is essentially treated by surgery associated with conventional chemotherapy or by chemotherapy alone when metastatic. Its poor prognosis, with less than 10% survival, is due to frequent relapses in metastatic forms even after multimodal therapy. This relapse is associated with the persistence of a cell subpopulation that has acquired or possesses intrinsic mechanisms to resist chemotherapeutic drugs. Indeed, gastric carcinoma, as other solid tumors, is heterogeneous and, a part of their cell population, the gastric cancer stem cells (GCSCs) are responsible for tumor initiation, progression,

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

recurrence, and metastasis. Herein, we first review the major markers of stem/progenitor cells in the stomach, then we describe the cells at the origin of gastric tumors, and finally, we focus on the characterization of the GCSC subpopulation.
