CD274 and neoplasm: We previously demonstrated that luminal flow, but not transmural flow, promotes tumor cell extravasation potential in vitro.[18] Also, the shear stress due to luminal flow acting in healthy, normal tissues is likely to be higher than in the tortuous, somewhat dysfunctional vascular networks in tumors.[13, 14] Yet, healthy tissues express lower endothelial PD‐L1 than tumor tissues.