Considering the low intratumoral T cell infiltration and lack of an IFNγ immune signature related to an adaptive immune response, including missing expression of T cell exhaustion markers, PD-L1 expression in NET G1/G2 and NET G3/NEC might be tumor-intrinsic and regulated by oncogenic pathways like MAPK, PI3K/PTEN, and p53, rather than reflecting an immune active tumor microenvironment [37,38,39]. Here, CD274 is linked to neuroendocrine carcinoma.