SMAD4 and lung cancer: NSCLC includes lung squamous cell carcinoma and adenocarcinoma and accounts for more than 80% of lung cancers.[19] With the development of surgery, chemotherapy, molecular targeted therapy and immunotherapy, promising advances in NSCLC treatment have been made, but the prognosis is still poor.[20,21] Recently, the clinicopathological and prognostic significance of SMAD4 expression in NSCLC patients was studied, but the conclusion is still controversial.