Department of Dermatology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China.

Introduction Programmed death-1 (PD-1) is an inhibitory T-cell receptor expressed by activated T-lymphocytes, and its two major ligands are PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC, CD273). Under normal conditions, PD-L1 is mainly expressed on T cells, B cells, den-dritic cells, and macrophages, whereas PD-L2 is expressed selectively on activated dendritic cells, macrophages, marrow-originated mast cells, and peritoneum B1 cells. However, malignant neoplasms, including lymphoma, non-small cell lung cancer (NSCLC), melanoma, renal cell carcinoma, and prostate cancer, can also overexpress PD-L1, which attenuates lymphocyte-mediated immune responses within the tumor and eventually leads to immune evasion. PD-1 inhibitors are effective in the treatment of tumors because they not only enhance the antitumor effect of the T cells, but also increase T-cell infil-tration[1]. In recent years, promising indications of activity for PD-1-targeted immunotherapy have been observed in clinical trials of cutaneous malignant neoplasms, including cutaneous T-cell lymphoma (CTCL), melanoma, Merkel cell carcinoma (MCC), basal cell carcinoma (BCC), and squamous cell carcinoma��SCC��. This new therapy is beneficial in the treatment of cutaneous neoplasms that are in need of more effective management.