PDCD1 and neoplasm: In a study on gastric cancer, patients with low PD-1+ macrophage expression (PD-1+ macrophage < 0.85%) and high PD-1+ macrophage expression (PD-1+ macrophage ≥ 0.85%) exhibited five-year disease survival rates of 85.9% and 65.8%, respectively, suggesting that increased PD-1-positive macrophages in tumor tissues are associated with poor prognosis (50).