Histological transformation from non‐small cell to small cell lung carcinoma after treatment with epidermal growth factor receptor‐tyrosine kinase inhibitor

Abstract

Several cases of acquired resistance in patients with activating epidermal growth factor receptor (EGFR) mutation have been reported. However, rare clinical cases exist of a transformation to small cell lung cancer (SCLC) following treatment with EGFR-tyrosine kinase inhibitors (TKIs). We report a case of non-small cell lung cancer (NSCLC) with L858R mutation at the time of diagnosis. After failure of EGFR-TKI therapy, we performed additional histopathologic examinations. We confirmed that the patient had a histological transformation from NSCLC to SCLC. We performed chemotherapy with etoposide and cisplatin against the SCLC and radiologic findings were improved.