Furthermore, biallelic inactivation of the tumor suppressor genes TP53 and RB1 are commonly observed.3, 4, 5, 6 Pulmonary neuroendocrine (NE) cells and certain epithelial cells are thought to be progenitors of SCLC, while these tumors can also arise from pretreated, epidermal growth factor receptor (EGFR)-mutated or anaplastic lymphoma kinase (ALK)-translocated lung adenocarcinomas through transdifferentiation in selected cases.7 This evidence concerns the gene ALK and small cell lung carcinoma.