RB1 and small cell lung carcinoma: Thus, despite the fact that type II LCNECs and some SCLCs harbor bi-allelic loss of TP53 and RB1, their transcriptional signatures include low levels of neuroendocrine genes and a distinct profile of NOTCHhigh and ASCL1low/DLL3low, which differentiates these tumors from type I LCNECs and from the majority of SCLC cases.