NEUROD1 and small cell lung carcinoma: Our scRNA-seq results revealed the co-expression or mutually exclusive patterns of key TFs, most commonly ASCL1 and NEUROD1. Our data also revealed a cell population in nearly all SCLC tumors with varying ratios that expressed none of these four TFs, implying plasticity between subtypes or even from different cell origins.45–47 The results also suggested that there might be exceptions of SCLC cases at the bulk level, despite rare, that are beyond the current subtypes and dominated by other TFs and thus need to be further specified.