TTF1 and adenocarcinoma: A previous study reported that patients who responded to first‐generation EGFR‐TKI had high serum CEA levels, TTF‐1‐positive tissue immunostaining, and were nonsmokers [15], all these findings suggestive of adenocarcinoma, indicating that patients who respond to EGFR‐TKI may also have adenocarcinoma components.