According to RNA expression with validation at the protein levels of the transcription factors ASCL1, NEUROD1, POU2F3, and YAP1, four SCLC subtypes have emerged: SCLC-A (ASCL1-driven), SCLC-N (NEUROD1-driven), SCLC-P (ASCL1/NEUROD1-double negative with POU2F3 expression), and SCLC-Y (YAP1-related and NOS) and SCLC-I (inflamed gene signature), which share the last subtype [65–69]. The gene discussed is POU2F3; the disease is small cell lung carcinoma.