CD274 and cholangiocarcinoma: As many aspects of PD-L1 testing in association with CCA have not been addressed systematically so far, we conducted this study i) to evaluate the expression levels of PD-L1 in CCA ii) to compare three different and commonly used antibodies against PD-L1 (clones 28–8, SP142 and SP263) and iii) to correlate PD-L1 expression levels with clinicopathological data, including overall survival.