BACKGROUND AND AIM: Thyroid transcription factor-1 (TTF-1) is a good prognostic factor and is also thought to be associated with driver mutations in lung cancer. This study aimed to evaluate the relationship between TTF-1 expression and prognosis and driver mutations in lung adenocarcinomas.

METHODS: We analyzed the data of 307 patients who were diagnosed with lung adenocarcinoma and underwent TTF-1 testing in two centers between January 2018 and January 2021.

RESULTS: Of the 307 patients included in the study, 231 were TTF-1 positive, 23 were weakly positive, and 53 were negative. There was no statistically significant relationship between TTF-1 positivity and progression-free survival (PFS) (p=0.492). However, overall survival (OS) was significantly longer in TTF-1 positive patients (p=0.005). Both PFS and OS were significantly longer in TTF-1 positive patients with multiple metastates (p=0.001, p=0.013). Of the 199 patients who underwent epidermal growth factor receptor (EGFR) mutation analysis, EGFR positivity was detected in 62 of them, and 58 patients were found to be in the TTF-1 positive group (p=0.022).

CONCLUSIONS: Thyroid transcription factor-1 positivity in lung adenocarcinomas is a good prognostic factor that often accompanies EGFR positivity.