CD274 and breast cancer: A breast cancer study using the mouse monoclonal antibody 130021 to detected PD-L1 found 69% (11/16) hormone sensitive breast cancer patients positive for CTCs (defined as ≥1 CTCs per 7.5ml blood, CellSearch) of those 72% (8/11) had PD-L1 positive CTCs with a range of 0.2–100% being PD-L1 positive [41].