Advances in novel molecular typing and precise treatment strategies for small cell lung cancer.

Small cell lung cancer (SCLC) is a high-grade neuroendocrine (NE) cancer characterized by high circulating tumor-cell burden and early extensive metastasis. Considering the complexity of SCLC genes and the immune microenvironment, their unique molecular heterogeneity profiles have been continuously explored. The understanding of SCLC subtypes has recently changed from traditional "classical" and "variant" types to "NE" and "non-NE" phenotypes and to the subtypes defined by major transcriptional regulators, which indicates the gradual revelation of high intratumoral heterogeneity and plasticity characteristics of SCLCs. Advances in genomics as well as the development of single-cell sequencing analysis and new preclinical models have helped investigators gain many new insights into SCLCs and the development of targeted therapy and immunotherapy strategies. This article provides an overview of changes in molecular typing, tumor heterogeneity, and plasticity and that of advances in the precise treatment of different subtypes of SCLC.