KRAS gene mutations are found in 20-30% of non-small cell lung cancer (NSCLC), especially in adenocarcinoma. Compared to EGFR and ALK mutations, KRAS mutation in NSCLC may be associated with poorer prognosis. However, prognostic value of different KRAS mutation subtypes in NSCLC remains unknown. The goal of this study is to evaluate the association of KRAS mutation subtypes, PD-L1 expression and clinical outcome in patients diagnosed with primary lung adenocarcinoma.