ASCL1 and small cell lung carcinoma: SCLC has been traditionally divided into “classic” and “variant” morphological subtypes [13], with morphological differences being driven by differential expression of achaete-scute homolog 1 (ASCL1), also known as ASH1, and neurogenic differentiation 1 (NeuroD1), two master transcription factors that govern neuroendocrine differentiation [14].