POU3F2 and small cell lung carcinoma: The four molecular subtypes of SCLC include SCLC-A, SCLC-N, SCLC-P, and SCLC-Y, which express achaete-scute homolog 1 (ASCL1), neurogenic differentiation factor 1 (NEUROD1), POU class 2 homeobox 3 (POU2F3), and yes-associated protein 1 (YAP1), respectively.