ASCL1 and small cell lung carcinoma: SCLC can be classified into four subtypes based on elevated expression of key transcription factors [15]: achaete-scute family bHLH transcription factor 1 (ASCL1) in SCLC-A, neuronal differentiation 1 (NEUROD1) in SCLC-N, Yes1 associated transcriptional regulator (YAP1) in SCLC-Y, and POU class 2 homeobox 3 (POU2F3) in SCLC-P.