CD274 and esophageal squamous cell carcinoma: Data on expression rates and prognostic value of PD-L1 immunohistochemistry in ESCC is rather scarce and partially conflicting, as some studies associate PD-L1 positive ESCC with poor patient outcome [24, 25, 32], while two recent studies [21, 22] demonstrated PD-L1 positivity to be predictive of a rather favorable disease course.