Another theory is that a greater immune response is yielded in small bowel NEN compared to pancreas NEN, however, a trial by the Dana-Farber Cancer Institute investigating archival NEN tumour specimens seems to contradict this theory as they observed larger presence of T-cell infiltrates in the extratumoural compartment pNEN than in small bowel NEN and a similar low PDL1 expression in both cancer subtypes [46]. This evidence concerns the gene CD274 and medical procedure.