Ren M, et al. - This study investigated the clinical effect of programmed death-ligand 1 (PD-L1) expression in primary acral melanoma. Immunohistochemistry was used to assess PD-L1 expression in tumor cells and tumor-infiltrating lymphocytes (TILs) as well as examining its relationships with clinicopathological features and survival in 78 primary acral melanoma patients. The present data indicated that PD-L1 expression in TILs, but not that in tumor cells, was an independent predictor of poor prognosis in acral melanoma, and this is the first study to do so.