CLDN1 was positive in 100% of oral and pharyngeal cancer, 94% of esophageal cancer, 93% of lung squamous cell carcinoma, 80% of gastric cancer, 93% of biliary tract cancer, 100% of pancreatic cancer, 100% of colorectal cancer, 94% of ovarian cancer, 100% of uterine cancer, and 100% of hepatoblastoma, as well as 65% of hepatocellular carcinoma, 44% of lung adenocarcinoma, 40% of nephroblastoma: Wilms tumor, and 33% of germ cell tumor. This evidence concerns the gene CLDN1 and biliary tract cancer.