Previous studies have demonstrated that serum tumor markers were related to histological type with significantly higher carcino embryonie antigen (CEA) serum levels in adenocarcinomas, squmaous cell carcinoma antigen (SCC-Ag) and cytokeratin 19 fragments (CYFRA21-1) in SCC and neuron specific enolase (NSE) in SCLC [16]. The gene discussed is ENO2; the disease is adenocarcinoma.