ASCL1 and small cell lung carcinoma: To develop more effective molecular targeted therapies, Rudin et al. recently proposed the classification of SCLC into four molecular subtypes based on the expression of the following key transcription and co-transcription factors: achaete-scute homologue 1 (ASCL1), neurogenic differentiation factor 1 (NEUROD1), yes-associated protein 1 (YAP1), and POU class 2 homeobox 3 (POU2F3) [11].