[Pathological and Molecular Biological Classification of Small Cell Lung Cancer]

The name of small cell carcinoma is becoming unified with neuroendocrine carcinoma in many other cancers except lung cancer, and following this trend, small cell carcinoma of the lung categorized into a subtype under neuroendocrine carcinoma in the 2015 WHO classification. However, small cell carcinoma has been retained and remain as a distinct entity. In this article, I introduced the history and current concept of small cell lung cancer classification, as well as the molecular biological classification of small cell lung cancer based on 4 definitive molecules, ASCL1, NEUROD1, YAP1, and POU2F3, proposed in 2019.