Compelling evidence in non-small-cell lung cancer (NSCLC) and melanoma suggests significant inter-assay heterogeneity in comparative studies of PD-L1 IHC tests due to geographical heterogeneity in PD-L1 expression, antibody used and interpretation.3,4 While considerable research efforts are underway to harmonise PD-L1 IHC assays in other solid tumours,5 the performance of the various PD-L1 IHC assays available is unknown in HCC. This evidence concerns the gene CD274 and melanoma.