Sialosyl‐Tn expression in benign and neoplastic proliferative lesions of the colon: of questionable value in predicting dysplasia

Abstract

Tumour-associated carbohydrate antigen expression patterns have been observed to change during the transformation from benign to dysplastic and malignant cells. Sialosyl-Tn is an O-linked mucin-type tumour-associated antigen expressed on glycoproteins and is the product of aberrant glycosylation of the Tn glycoprotein, an early precursor of the MN blood group antigen. Sialosyl-Tn expression has been observed in adenomas and carcinomas of the colon as well as in dysplastic lesions in ulcerative colitis (UC). Sialosyl-Tn expression has been proposed to be a prognostic marker for the development of dysplasia in UC. To evaluate Sialosyl-Tn expression in benign and malignant proliferative lesions of the colon, and its relevance for prediction of dysplasia, we immunostained cases of adenoma, adenoma with invasive carcinoma, UC with and without dysplasia, hyperplastic polyps, cases of lymphocytic colitis, and cases of acute self-limited colitis with antibody against Sialosyl-Tn. We found expression of Sialosyl-Tn in dysplastic lesions in adenomas and UC. We also found expression of Sialosyl-Tn in epithelium of chronic colitis in virtually all patients with UC, both with dysplasia and without. Sialosyl-Tn was also present in hyperplastic polyps, and one single case each of lymphocytic colitis and acute self-limited colitis. We conclude that Sialosyl-Tn is expressed in dysplastic and malignant epithelial lesions of the colon. Expression of Sialosyl-Tn in benign proliferative/regenerative lesions in the colon is frequent and is not directly related to the development of dysplasia. Possible mechanisms of Sialosyl-Tn expression are discussed.