ASCL1 and small cell lung carcinoma: While SCLC with upregulated achaete‐scute family bHLH transcription factor 1 (ASCL1) or neuronal differentiation 1 (NEUROD1) expression is a classic type with a neuroendocrine (NE) feature, other SCLC subtypes lack NE features, making SCLC a highly heterogeneous tumor [7, 8, 9, 10, 11].