POU2F3 and small cell lung carcinoma: The classification is based on the differential expression of four transcription regulators: ASCL-1, NEUROD1, POU2F3 and YAP1. Based on RNA-expression of those markers, the subclassifications of SCLC-A, SCLC-N, SCLC-P and SCLC-Y was introduced and could be used to identify therapeutic weaknesses and challenges [10].