RB1 and small cell lung carcinoma: According to these findings it was proposed a model of progressive development of murine SCLCs, starting from Pulmonary Neuroendocrine Progenitors through intermediate Neuroendocrine Hyperplasia to SCLC through the progressive acquisition of driver mutations mainly represented by RB1 deletion, TP53 deletion, MYCL amplification and PTEN mutation [268].