PDCD1 and gastric adenocarcinoma: Immune‐checkpoint molecules PD‐1, LAG3, CTLA4, TIGIT, and HAVCR2 (TIM‐3) have been identified and studied in various cancers including liver hepatocellular carcinoma, lung adenocarcinoma, stomach adenocarcinoma, ovarian cancer, and peritoneal carcinoma.59, 60