While PD-L1expression is widely considered a predictive biomarker for response to PD-1/PD-L1 inhibitors in several solid tumors—including non-small cell lung cancer, urothelial carcinoma, and head and neck squamous cell carcinoma—its relevance in neuroendocrine neoplasms (NENs) remains uncertain [33–35]. Here, CD274 is linked to head and neck squamous cell carcinoma.