['Yes-associated protein (YAP) has been reported to be associated with the prognosis of various cancers and also to affect epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) activity in ovarian cancer cell lines. However, few studies have evaluated YAP protein expression in lung cancer, and the results have lacked consistency.', 'YAP expression was evaluated in a total of 205 curatively resected lung adenocarcinomas and 36 cases of EGFR-mutated TKI-treated patients. Correlations between the expression of YAP and clinicopathologic features, response to EGFR-TKI treatment, and prognostic significance were analyzed.', 'High cytoplasmic YAP expression was positively correlated with the clinicopathologic parameters that have been associated with favorable prognosis. Multivariate analysis revealed that high cytoplasmic YAP expression was an independent prognostic factor in lung adenocarcinomas (progression-free survival: hazard ratio [HR] 0.659; 95 % confidence interval [CI] 0.431-1.010; p = 0.050; overall survival: HR, 0.474; 95 % CI 0.263-0.854; p = 0.013) and EGFR-TKI-treated patients with EGFR mutation (progression-free survival: HR, 0.346; 95 % CI 0.146-0.818; p = 0.016; overall survival: HR, 0.291; 95 % CI 0.125-0.676; p = 0.004).'] Is cytoplasmic YAP expression associated with prolonged survival in patients with lung adenocarcinomas and epidermal growth factor receptor tyrosine kinase inhibitor treatment?