CD274 and neoplasm: The frequency of high TMB, PDL1 expression and MSI-high amongst CUP tumours has been evaluated by a few studies, which suggest one or more of these biomarkers may be present in up to 28% of cases.55,59,73 Determining a potential immunotherapy-responsive subgroup of CUP is hampered by a lack of validated predictive biomarkers and further research is desperately needed.