We herein describe a discrepancy between the clinical image and pathological findings in a non-small cell lung cancer patient with an epidermal growth factor receptor (EGFR) mutation who underwent surgical resection after gefitinib treatment. The patient was a 66-year-old female with c-stage IIIA lung adenocarcinoma harboring an EGFR gene mutation; she was surgically treated after receiving gefitinib. The pathological examination revealed adenocarcinoma, and the pathologically therapeutic effect was considered to be slight or of no response. EGFR T790M mutation and MET amplification were not present. The pathologically therapeutic effect is generally well correlated with the response rate after induction therapy. In this case, there was a discrepancy between the clinical image and pathological findings. Our findings, therefore, raise questions about the role of surgery after EGFR-tyrosine kinase inhibitor treatment.