Additional studies investigating the role of the PD-1/PD-L1 axis in NB demonstrated a large variation in PD-L1 expression, where decreased survival and increased risk of relapse was noted in high-risk and INSS stage 4 NB tumors that expressed PD-L1, whereas no differences in clinical outcome were noted in more differentiated tumors graded as INSS stage 1/2/3 or those with low- and intermediate-risk [133, 134]. This evidence concerns the gene CD274 and neuroblastoma.