A rare case of double primary lung adenocarcinomas with uncommon complex EGFR G719X and S768I mutations and pleomorphic carcinoma.

Epidermal growth factor receptor‐tyrosine kinase inhibitor (EGFR‐TKI)‐targeted therapy has emerged as a viable treatment for patients with advanced non‐small cell lung cancer with common EGFR mutations. The uncommon G719X and S768I mutations can co‐occur as complex mutations in the same tumor. Here we report a case of a 72‐year‐old male patient with double lung carcinoma, with G719X and S768I complex mutations detected in the right upper lung lobe along with brain metastases. Osimertinib (80 mg/day) was administered as the first‐line treatment, and a reduction in the right lobe tumor and brain lesions was achieved. However, the left upper lung lobe mass remained unchanged; histopathological examination via a lobectomy revealed pleomorphic carcinoma. Thus, the patient was diagnosed with multiple primary lung cancers. In conclusion, osimertinib is a viable treatment option for lung cancer with rare EGFR G719X and S768I complex mutations. [ABSTRACT FROM AUTHOR]