 specif carcinoembryon antigen human digest system wide varieti human adult fetal tissu studi immunodiffus techniqu agar gel determin contain tumor-specif antigen colon cancer adult tissu demonstr ident antigen test specimen malign tumor entoderm deriv epithelium gastro-intestin tract pancrea absent test adult tissu common antigen constitu repres system-specif cancer antigen human digest system system-specif cancer antigen demonstr human experi fetal tissu demonstr ident antigen fetal gut liver pancrea 2 6 month gestat compon name carcinoembryon antigen human digest system basi find work control express genet potenti genet potenti type cell conclud carcinoembryon antigen repres cellular constitu repress cours differenti normal digest system epithelium reappear correspond malign cell process derepress-dedifferenti 