CD9 and adenocarcinoma: The CD9 positive expression ratio of cases with well-differentiated adenocarcinoma, the largest tumor diameter <2 cm, lymph node without metastasis and organs, which did not invade surrounding tissues, was significantly higher than that of cases with the poorly differentiated adenocarcinoma, the largest tumor diameter ≥2 cm, lymph node with metastasis and organs invading surrounding tissues.