Immunoreactivity of tumor-associated glycoprotein (TAG-72) in normal, hyperplastic, and neoplastic colon

Monoclonal antibody B72.3 recognizes tumor-associated glycoprotein (TAG-72) and has been widely used to identify malignant epithelial cells in cytologic and histologic preparations. We investigated TAG-72 expression in normal, hyperplastic, and neoplastic adult colon tissues. Formalin-fixed, paraffin-embedded samples of normal (43), hyperplastic (20), and neoplastic (70) colonic tissue were studied with B72.3 using the avidin-biotin complex immunoperoxidase method. TAG-72 expression was detected in 100% of the invasive carcinomas, in 84% of the normal colon samples, in 100% of the hyperplastic polyps, and in 93% of the adenomatous or mixed hyperplastic-adenomatous lesions. Among cases expressing TAG-72 immunoreactivity, the extent of staining varied from 100% of cells in normal and hyperplastic lesions to 10% to 100% in neoplastic lesions. A consistent supranuclear (presumably Golgi) staining pattern was observed in all tissues with the exception of carcinoma and some adenomas; in these cases, staining localized to the luminal surface and intraluminal mucin and/or was diffusely cytoplasmic. From these data, it is clear that TAG-72 is expressed in both benign and neoplastic cells of the human adult colon, although different patterns of expression may distinguish malignant transformation. Furthermore, carcinoma cells less consistently express TAG-72, so that small biopsies or cytologic specimens may be falsely negative due to sampling errors.