PTGER4 and adenocarcinoma: Wang et al. [17] found that the positive rate of SHOX2 gene methylation in LC patients was related to pathological type and TNM stage, in which the higher the adenocarcinoma and TNM stage, the higher the methylation positivity rate, which was basically consistent with the results of the present study, confirming that there is a correlation between the positive detection rate of SHOX2, RASSF1A and PTGER4 gene methylation and the clinicopathological features of LC patients.