CD274 and large cell neuroendocrine carcinoma: reported a single case of patient with stage IB LCNEC (PD-L1 negative but positive for PD-L1 amplification and tumor mutation burden high) who progressed after adjuvant chemotherapy after surgery; subsequently, the patient was treated with pembrolizumab, and after one cycle, all visible lesions shrunk, and no new lesions were seen.