PD-L1 immunohistochemistry (IHC) staining was performed on eight tumors, including two seminomas and six non-seminomas, which demonstrated overall positivity of 75% of the tumors measured, with a 60% (3/5) positivity at stage I and 100% (3/3) positivity at stage III (Supplementary Table S1). This evidence concerns the gene CD274 and seminoma.