Abstract
Backgrounds. EGFR-tyrosine kinase inhibitors (TKIs) are key drugs for the treatment of EGFR mutation-positive lung cancer. However, resistance will eventually be acquired, and one mechanism for this acquisition is transformation. Case. A 71-year-old man with post-operative recurrent lung adenocarcinoma harboring EGFR exon 19 deletion received afatinib, and a partial response was achieved. However, multiple lung nodules and mediastinum lymphadenopathy were detected. Progressive disease was suspected, so he underwent transesophageal endoscopic ultrasound-guided fine needle aspiration. The specimen showed non-small-cell lung cancer with neuroendocrine morphology and positive neuroendocrine markers, possible large-cell neuroendocrine carcinoma (LCNEC). LCNEC was clinically diagnosed, and the EGFR mutation was negative. Double cancer of adenocarcinoma and LCNEC, not transformation, was diagnosed. Conclusion. Transformation during EGFR-TKI therapy has been reported, but double cancer has never been described previously. Because the treatment strategy is different, it is important to differentiate double cancer from transformation.
