RASSF1 and adenocarcinoma: The results of this study showed that among different pathological types and TNM staging, the methylation positivity rates of SHOX2 and RASSF1A genes were highest in adenocarcinoma and LC patients with TNM stage IV, and the methylation positivity rate of PTGER4 gene was highest in LC patients with TNM stage IV, which indicated that the methylation positivity rates of SHOX2 and RASSF1A genes in LC patients were related to their pathological types and TNM staging, while PTGER4 gene methylation positivity was only associated with TNM staging.