A new classification of SCLC subtypes has been defined by differential expression of four key transcription regulators: achaete-scute homologue 1 (ASCL1; also known as ASH1), neurogenic differentiation factor 1 (NeuroD1), yes-associated protein 1 (YAP1) and POU class 2 homeobox 3 (POU2F3) [67]. This evidence concerns the gene YAP1 and small cell lung carcinoma.