CD274 and thymoma: However, consistent with previous literature, PD-L1 amplification did not always correlate with high positive PD-L1 expression in IHC analysis.29 In this study, 6 out of 7 (85.7%) of the HL patients, 1 NK/T lymphoma patient, 1 melanoma and 1 thymoma patient showed high levels of PD-L1 expression in IHC analysis.