POU2F3 and small cell lung carcinoma: Recent data, however, demonstrated that SCLC tumors could be sub-segmented into distinct molecular subtypes based on the expression pattern of specific transcription factors (achaete-scute homologue 1 (ASCL1), neurogenic differentiation factor 1 (NEUROD1), POU Class 2 homeobox 3 (POU2F3)) and inflammatory characteristics.