CD274 and small cell lung carcinoma: This review examines three key advances reshaping SCLC management: (1) mechanistic links between DLL3-driven tumorigenesis and PD-L1-mediated immunosuppression, (2) clinical progress in antibody-drug conjugates (ADCs) with next-generation payloads (e.g., FZ-AD005), multispecific BiTEs (e.g., HPN328), and engineered CAR-T/NK cells with enhanced metabolic resilience, and (3) precision strategies combining liquid biopsy for dynamic DLL3 profiling with immuno-PET imaging using [89Zr]Zr-DFO-SC16.