Lectin histochemistry of colonic adenomas

34 adenomas of the colon and adjacent flat mucosa were reexamined by morphological, histochemical and immunohistochemical means. Adenomas were grouped according to the degree of epithelial cell atypia: group 1 (dysplastic adenomas) showing mild and moderate dysplasia and group 2 (cancerous adenoma) with severe dysplasia and carcinoma. Morphological and secretive changes (hyperplasia with hypersialomucin secretion), considered typical of 'transitional mucosa', were constantly found in the adjacent and stalk mucosa. A panel of six lectins were tested using PAP and ABC system methods to compare amount and cytoplasmic localization of labelling sites with the morphological changes such as hyperplasia, dysplasia and carcinoma. All the tested lectins were reactive in up to 90% of adenomas as well as in adjacent mucosa. Positivity was unrelated to the severity of dysplasia and no preferential localization of labelled sites was shown in the adenoma groups. However, cytoplasmic distribution of reactivity was quite different in hyperplastic epithelium compared to dysplastic ones.