NEUROD1 and small cell lung carcinoma: SCLC is a heterogeneous tumor, comprising both neuroendocrine (NE) and non-neuroendocrine (non-NE) cells, further classified into four subtypes (SCLC-A, SCLC-N, SCLC-P, SCLC-Y) based on the expression of lineage-defining transcription factors ASCL1, NEUROD1, POU2F3, and YAP1(Rudin et al. 2019).