TTF-1 and EGFR expression are related to EGFR mutation in lung adenocarcinoma

Thyroid transcription factor-1 (TTF-1) is routinely used in the diagnosis of lung carcinoma and the subclassification of non-small cell lung cancer (NSCLC) in combination with other markers. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are particularly effective in NSCLC patients harboring active EGFR mutations. EGFR protein is a poor prognostic factor for NSCLC patients. The relationship between TTF-1 expression and EGFR mutation and EGFR expression has not been well documented. The aim of this study was to investigate the relationship between TTF-1 and EGFR expression and mutation, and the clinical significance in lung adenocarcinoma. We analyzed TTF-1 expression, EGFR expression and mutation in 213 cases of lung adenocarcinoma. TTF-1 and EGFR expression levels were detected by immunohistochemical staining with monoclonal antibodies. EGFR mutations in exon 18, 19, 20 and 21 were assayed by the scorpion amplification refractory mutation system (ARMS) method. Forty-eight patients with EGFR mutations in exon 19 or 21 were detected from 91 patients with TTF-1 strong positive expression (3+) (52.74%), and 35 patients were detected with either exon 19 or 21 mutations from 54 patients with both TTF1 and EGFR positive expression (64.81%). Our data indicate that TTF-1 expression was positively related to EGFR mutation (P < 0.001) and EGFR expression (P < 0.001). EGFR expression level was positively related to its mutation (P = 0.003). These results indicate TTF-1 and EGFR positive lung adenocarcinomas frequently harbor EGFR mutations.