MAPK3 and adenocarcinoma: The positive staining for p-ERK1/2 or PI3-K was significantly lower in well/highly-differentiated adenocancinomas with maximal diameter < 2.0 cm, no metastasis to lymph node, and no infiltration of regional tissues or organs compared to poorly-differentiated adenocarcinomas which are characterized by a maximal diameter ≥ 2.0 cm, with metastasis to lymph node and infiltration of regional tissues or organs (P < 0.05 or P < 0.01).