This framework introduced a clear biological dichotomy between neuroendocrine (NE)-high (comprising SCLC-A, SCLC-N) and NE-low (comprising SCLC-P, SCLC-Y) subgroups, each driven by its respective transcription factor (ASCL1, NEUROD1, POU class 2 homeobox 3 (POU2F3) and yes-associated protein 1 (YAP1), respectively). The gene discussed is ASCL1; the disease is small cell lung carcinoma.