EGFR and small cell lung carcinoma: Although some prior studies have suggested that inactivation of the tumor protein p53 (TP53) and retinoblastoma 1 (RB1) genes might be associated with the transformation of EGFR-mutated non-small cell lung cancer (NSCLC) to SCLC following TKI therapy (13, 14), the full clinicopathological characteristics and underlying molecular mechanisms of this transformation remain largely unexplored.