Concerning the clinicopathologic characteristics of lung adenocarcinoma and related EGFR phenotypes as well as CA9 SNP expression in the current study, the co-existence of CA9 SNP rs2071676 and EGFR wild type were significantly associated with both the lower tumor stage and lower risk for developing lymph node metastasis of lung adenocarcinoma whether in the whole study population or the male population. This evidence concerns the gene CA9 and lung adenocarcinoma.