CD44 and gastric cancer: Classical CD44 molecules are intimately involved in the pathogenesis of malignancies such as esophageal cancer, breast cancer, gastric cancer, and prostate cancer [4, 5, 7] CD44 has also been reported as a marker of CSCs in prostate, breast, and head and neck cancer and its expression in these tumors is associated with poor prognosis and aggressive behavior [4, 10, 11].