The human carcinoembryonic antigen antibody (CEA) family consists of glycophosphatidyl inositol (GPI) linkage and transmembrane linkage members. Studies suggest the GPI-linked members tend to be up regulated in human tumors, whereas the transmembrane-linked members tend to be down regulated. CEA (CD66e) [COL-1], a GPI-linked member, shows no detectable reactivity for other CEA members. [COL-1] may be useful in aiding the detection of early foci of gastric carcinoma and distinguishing pulmonary adenocarcinomas from mesothelioma. Studies have shown it stains many types of adenocarcinoma, but does not stain benign glands, stroma, or malignant prostatic cells.