More specific markers for colon cancer, in addition to CEA, are needed. Before extensive clinical trials are run on newly discovered markers, it is essential to define their cellular and subcellular localization to assure their validity as tumor markers. This laboratory has recently detected a new tumor marker in both primary and metastatic colon cancer using zinc glycinate extraction procedures, and antibodies produced in tolerant rabbits. This marker (ZGM) was found in addition to CEA; was immunochemically different from CEA; was not detectable in normal colonic mucosa; and anti-ZGM activity was not removed by absorption with liver, spleen, plasma, colonic mucosa, purified CEA and blood group substances (A,B,H,Lea and Leb). We propose to define the histological localization of ZGM in colo-rectal carcinoma utilizing immunofluorescent and immunohistochemical techniques, and to compare it with that of CEA. This will be done on tissues carefully dissected and histologically characterized. We will assess the specificity of ZGM for colo-rectal, and other carcinomas, and for premalignant lesions such as colonic polyps. Tissue levels of ZGM will be correlated with prognostic histopathological parameters, such as tumor differentiation, invasiveness and lymphocyte and plasma cell infiltration.