POU3F2 and small cell lung carcinoma: Of note, SCLC can be categorized into four subtypes named SCLC-A, SCLC-N, SCLC-P, and SCLC-Y, based on the expression of specific genes, namely achaete-scute homolog 1 (ASCL1), neurogenic differentiation factor 1 (NeuroD1), POU class 2 homeobox 3 (POU2F3), and yes-associated protein-1 (YAP-1), respectively (52, 53).