HIF1A and neoplasm: Several recent studies have described the expression of PD-L1 within tumor cells to be closely associated with accumulation of 2-deoxy-2-[fluorine-18] fluoro-D-glucose (18F-FDG) in positron emission tomography (PET), replacing hypoxia inducible factor 1α (HIF-1α) as an alternative marker [7–15].