NEUROD1 and small cell lung carcinoma: The identification of four SCLC subtypes—characterized by the differential expression of transcription factors (ASCL1, NEUROD1 and POU2F3) or low expression of all three transcription factor signatures accompanied by an inflamed gene signature (SCLC-A, N, P and I, respectively)—could lead to a better understanding of SCLC disease and could provide the right direction for more personalized treatment.