POU2F3 and small cell lung carcinoma: At present, SCLC is grouped into four subtypes based on specific transcription factors: ASCL1 (SCLC-A), NEUROD1 (SCLC-N), POU2F3 (SCLC-P), and YAP1 (SCLC-Y) (Borromeo et al., 2016; Huang et al., 2018; Rudin et al., 2019).