PDCD1 and skin squamous cell carcinoma: This meta-analysis of 26 studies (2012-2024) evaluated treatments for cutaneous malignancies, including melanoma, basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and Merkel cell carcinoma (MCC), covering systemic immunotherapies (PD-1, CTLA-4), combination checkpoint inhibitors, and novel approaches like IL-12 electroporation.