FISH analysis was performed in 308 randomly selected GC and GEJ adenocarcinoma cases, including 40 cases with HER2 overexpression (IHC 3+), 38 cases with equivocal (IHC 2+), and 230 cases with negative (IHC 1+/0) HER2 expression. The gene discussed is ERBB2; the disease is gastric cancer.