For example, CK7(-)/CK20(+) tumors may originate from colorectum, CK7(+)/CK20(+) tumors may originate from pancreas, biliary tract and gastroesophageal, etc., CK7(+)/CK20(-) tumors may originate from breast and ovary, etc., and CK7(-)/CK20(-) tumors may originate from hepatocellular carcinoma and squamous cell carcinoma (8, 21). This evidence concerns the gene KRT7 and squamous cell carcinoma.