NEUROD1 and small cell lung carcinoma: As shown in Figure 5, besides SCLC-A (ASCL1-defined), SCLC-AN (combined ASCL1/NEUROD1), SCLC-N (NEUROD1-defined), and SCLC-P (POU2F3-defined), the previously proposed quadruple negative SCLC subtype (SCLC-QN) was also identified in our cohort.