Studies in gastrointestinal NET primaries have shown variable results [36–38]; for example patients with grade 3 tumours showed higher PD-L1 expression (7/15; 46.7%) compared to grade 2 tumours (0/17; 0%) in a series of mixed hindgut and foregut NENs (including well- and poorly-differentiated tumours) [36]. Here, CD274 is linked to neoplasm.