NEUROD1 and small cell lung carcinoma: More recent evidence has defined a new classification model of SCLC subtypes, characterized by differential expression of the transcriptional regulators achaete-scute homologue 1 (ASCL1), neurogenic differentiation factor 1 (NeuroD1), yes-associated protein 1 (YAP1) and POU class 2 homeobox 3 (POU2F3) [24].