Although it was characterized as molecularly homogeneous due to loss of TP53 and RB1, and neuroendocrine/epithelial differentiation [27,28], SCLC was shown to be heterogeneous [29–37] by the identification of its mixtures of transcriptional subtypes such as neuroendocrine (NE) stem-cell-like subtype centered on the expression of the transcription factors ASCL1 and NEUROD1 [35] and non-neuroendocrine (NON-NE) subtype centered on the expression of the transcription factor YAP1 [36]. The gene discussed is NEUROD1; the disease is small cell lung carcinoma.