Immunohistochemical evaluation of carcinoembryonic antigen, secretory component, and epithelial IgA in tubular and villous large-bowel adenomas with different grades of dysplasia.

In a material of 513 consecutively collected large-bowel polyps, tubular and villous adenomas with corresponding histologic grades of epithelial dysplasia were selected. Fifty-two samples of the former and 27 of the latter category were evaluated semiquantitatively for immunohistochemical staining of the epithelial marker proteins carcinoembryonic antigen (CEA), secretory component (SC), and IgA. No consistent differences in the overall staining properties were found between the two types of tumours. In both categories the staining intensity for SC and epithelial IgA decreased with increasing degree of dysplasia, most strikingly so for IgA. This observation shows that the malignant alterations impair the capacity of the columnar epithelium to produce SC and to express it as a functional receptor mediating uptake of dimeric IgA. Thus, the absence of epithelial IgA in large-bowel adenomas may be a useful adjunct in grading of dysplasia. Conversely, the presence of CEA did not seem to be related to dysplastic alterations in the epithelium.