POU2F3 and small cell lung carcinoma: In the present multicenter study, we investigated the expression pattern, clinical significance, and prognostic relevance of subtype‐specific transcription factors (ASCL1, NEUROD1, POU2F3, and YAP1), as well as P53 and RB1 proteins in a large cohort of surgically treated SCLC patients comprising 386 samples.