ERBB2 and gastric cancer: We performed a prospective, multicenter, observational cohort study (JFMC44-1101) to evaluate HER2 expression and gene amplification in consecutively registered Japanese patients with metastatic (excluding curatively resected cases) or recurrent GC, and explored the clinicopathological features in relation to HER2 positivity (IHC score 3+ and/or FISH positive) or low HER2 expression (IHC score 0/FISH positive or IHC score 1+/FISH positive).