PD-L1 expression of the four microsatellite-unstable cases was heterogeneous: Two microsatellite-unstable cases (both intrahepatic cholangiocarcinomas) showed no PD-L1 expression, the other two microsatellite-unstable cases (both perihilar cholangiocarcinomas) showed minimal to moderate membranous and cytoplasmic PD-L1 expression (5% and 30% of all tumour cells, respectively; see supplementary figure). Here, CD274 is linked to neoplasm.