PDCD1 and neoplasm: Therefore, the aim of this study was to characterize the immune landscape in T-NEN with regard to the PD-1/PD-L1 pathway, tumor-infiltrating lymphocytes (TILs) [including helper T (Th) and cytotoxic T lymphocytes (CTLs)], and tumor-infiltrating myeloid cells (including monocytic and granulocytic cells).