In this manuscript, a global review on the gastric biomarker literature to date is undertaken, which is dedicated exclusively to the discussion of the role of biomarkers in GC, specifically HER2; E-cadherin; fibroblast growth factor receptor (FGFR)/human epidermal growth factor receptor family (EGFR)/mammalian target of rapamycin (mTOR)/hepatocyte growth factor receptor (HGFR, MET); PD-L1 expression; TP53; MSI; and emerging biomarkers including microRNAs, long noncoding RNAs (LncRNAs), and matrix metalloproteinases (MMPs) (Table 2). The gene discussed is ERBB2; the disease is gastric cancer.