YAP1 and small cell lung carcinoma: Although SCLC is considered as a molecularly homogeneous malignancy, recent analyses have led to the classification of molecular subtypes based on the intertumor heterogeneity of ASCL1, NEUROD1, POU2F3, and YAP1 expression: these subtypes are termed as SCLC-A, SCLC-N, SCLC-P and SCLC-Y.9 SCLC-A and SCLC-N are considered to be SCLC with neuroendocrine characteristics (SCLC-NE), in which SCLC-A represents the ‘classic’ subtype of SCLC-NE and SCLC-N represents the ‘variant’ subtype.