Thyroid transcription factor (TTF)-1 expression is a diagnostic marker and a good prognostic indicator for lung adenocarcinoma. However, its good prognostic ability might be due to epidermal growth factor receptor (EGFR)- sensitizing mutations as shown by the positive correlation between TTF-1 expression and EGFR mutations. | Thyroid transcription factor-1 as a prognostic indicator for stage IV lung adenocarcinoma with and without EGFRsensitizing mutations