ASCL1 and small cell lung carcinoma: Subtyping has emerged as a key concept in advancing personalised medicine for SCLC, Currently, SCLC is classified into four subtypes based on the expression of master transcription factors: Achaete-scute complex homologue 1 (ASCL1)-positive (SCLC-A), Neuronal differentiation 1 (NEUROD1)-positive (SCLC-N), POU class 2 homeobox 3 (POU2F3)-positive (SCLC-P), and Yes-associated protein 1 (YAP1)-positive (SCLC-Y) [3, 4].