Lung cancer is the leading cause of cancer related death, and is divided into two major histological subtypes, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Histological transformation from NSCLC to SCLC has been reported as a mechanism of treatment resistance in patients who received tyrosine kinase inhibitors (TKIs) targeting EGFR, ALK and ROS1 or immunotherapies. The transformed histology could be due to therapy-induced lineage plasticity or clonal selection of pre-existing SCLC cells. Evidence supporting either mechanism exist in the literature. Here, we discuss potential mechanisms of transformation and review the current knowledge about cell of origin of NSCLC and SCLC. In addition, we summarize genomic alterations that are frequently observed in both “de novo” and transformed SCLC, such as TP53, RB1 and PIK3CA. We also discuss treatment options for transformed SCLC, including chemotherapy, radiotherapy, TKIs, immunotherapy and anti-angiogenic agents.

肺癌是癌症相关死亡的主要原因，分为两种主要的组织学亚型：非小细胞肺癌（NSCLC）和小细胞肺癌（SCLC）。据报道，从 NSCLC 向 SCLC 的组织学转化是接受靶向EGFR、ALK和ROS1的酪氨酸激酶抑制剂 (TKI) 的患者的治疗耐药机制或免疫疗法。组织学的转变可能是由于治疗诱导的谱系可塑性或先前存在的 SCLC 细胞的克隆选择所致。文献中存在支持任一机制的证据。在这里，我们讨论潜在的转化机制，并回顾目前关于 NSCLC 和 SCLC 细胞起源的知识。此外，我们总结了在“从头”和转化 SCLC 中经常观察到的基因组改变，例如TP53、RB1和PIK3CA。我们还讨论了转化型 SCLC 的治疗方案，包括化疗、放疗、TKIs、免疫疗法和抗血管生成药物。