A 65-year-old man presented with cough and dyspnea and was diagnosed with stage IV EGFR exon 19 deletion well-differentiated lung adenocarcinoma (TTF-1+/CK7+), with metastases involving the right pleura, bilateral lungs, mediastinal lymph nodes, and bones (Fig. 2). This evidence concerns the gene TTF1 and lung adenocarcinoma.