CD274 and yolk sac tumor: The same comparison of frequency between the yolk sac component (N ═ 12), with the EC and seminoma shows that PD-L1 positive lymphocytes are a significantly more frequent feature of seminoma (P ═ 0.02), while between yolk sac tumor and EC, there is no significant difference in the PD-L1 positivity on either lymphocytes (P ═ 0.075) or tumor cells (P ═ 0.537) (Figure 6).