ASCL1 and small cell lung carcinoma: Recent studies have shown that the SCLCs family can be divided into four distinct subtypes based on the differential expression of four transcription factors (79); two of these subgroups, characterized by a high expression of ASCL-1 (SCLC-A) or NEUROD1 (SCLC-N), share a neuroendocrine phenotype; the other two subgroups can be divided on the basis of the expression of POU2F3 (SCLC-P) or of the lack of expression of the three transcription factors (SCLC-I).