CD274 and gastrointestinal stromal tumor: Although head and neck squamous cell carcinoma (HNSCC) and pancreatic adenocarcinoma contain the largest number of positive IHC stains (5 and 4, respectively), HNSCC (55.5%), TCC (50%), GIST (50%), and NET (50%) represent the greatest proportion of positive PD-L1 stains per cancer subtype.