PDCD1 and melanoma: After the groundbreaking approval of pembrolizumab for advanced melanoma treatment in 2014, the clinical utility of PD-1/PD-L1 inhibitors has expanded to various cancer types, including head and neck squamous cell carcinoma 106-108, non-small cell lung cancer (NSCLC) 109, and renal cell carcinoma (RCC) 110.