The characterization of the tumor microenvironment (TME), including tumor-infiltrating lymphocytes (TILs) CD3+ and CD8+, represents another independent biomarker, even though the heterogeneity between primary tumor and metastatic lesions as well as the difficulty of biopsy in some patients makes its use unsatisfactory for monitoring the efficacy of ICIs [34,37]. Here, CD8A is linked to neoplasm.