CD4 and Patent ductus arteriosus: Although enhanced PD‐L1 expression on cancer cells was seen in the hot spot area of CD4+ or CD8+ lymphocyte infiltration in 6 of 11 (54.3%) PD‐L1 positive samples (Fig. S1), there was no significant correlation between PD‐L1 expression by PDA cells and the number of infiltrating CD4+ or CD8+ cells.