CD274 and Patent ductus arteriosus: When patients were divided into four groups according to PD‐L1 and HLA class I expression, negative PD‐L1 expression and high HLA class I expression by PDA (n = 12) was associated with a significant better recurrence‐free survival (P < 0.001; Fig. 5A) and overall survival (P = 0.049; Fig. 5B) compared with patients HLA class I high and PD‐L1 positive (n = 5), HLA class I low and PD‐L1 negative (n = 13), or HLA class I low and PD‐L1 positive (n = 6) tumors.