TP53 and neoplasm: SCLC is a highly aggressive, invasive, and lethal form of lung cancer compared to NSCLC, frequently metastasizing to distant organs such as the brain, skeletal system, and lymph nodes and characterized by rapid tumor growth, high vascularity, genomic instability, early metastatic dissemination, almost universal inactivation of TP53 and RB1, and frequent disruption of several characteristic signaling networks.