Further stratified analysis by histological subtypes demonstrated that CD9 mRNA levels were markedly higher in esophageal squamous cell carcinoma (ESCC) than in esophageal adenocarcinoma (EAC) (P<0.0001, Figure 1B), suggesting a potential subtype-specific role of CD9 in ESCC pathogenesis. Here, CD9 is linked to esophageal adenocarcinoma.