As the most metastatic, treatment-resistant, and fatal form of lung cancer,4,5 SCLC exhibits a high degree of intratumoral heterogeneity, harboring cells of NE and non-neuroendocrine (non-NE) states,6,7,8,9,10,11,12 further defined by differential expression of lineage-defining transcription factors ASCL1, NEUROD1, and POU2F3. A fourth subtype has been characterized by YAP1 expression9,11,13,14,15 or low expression of all three transcription factors accompanied by an inflamed gene expression program.16 Here, ASCL1 is linked to small cell lung carcinoma.