SIMPLE MUCIN-TYPE CARBOHYDRATE ANTIGENS (T, SIALASYL-T, TN AND SIALOSYL-TN) IN BREAST CARCINOGENESIS

Immunohistochemical analysis of the expression of simple mucin-type ca rbohydrate antigens (Tn, sialyl-Tn and T) was performed in a series of 43 cases of intraductal hyperplasia without atypia, 9 cases of intrad uctal hyperplasia with atypia, 54 cases of ductal carcinoma in situ (D CIS) and 26 cases of invasive breast carcinoma. We also studied 36 cas es of isolated breast normal epithelium, 20 cases of ''normal'' breast epithelium adjacent to neoplasms and 14 cases of apocrine metaplasia. All antigens were detected in different frequencies in normal, hyperp lastic, metaplastic and neoplastic breast epithelium. Tn and sialyl-Tn are expressed more frequently in malignant than in benign breast epit helium; while Tn expression increases from normal to invasive carcinom as, sialyl-Tn increases until DCIS and drops in invasive carcinomas, s uggesting that either there is a failure of a proportion of DCIS to pr ogress to invasive carcinoma or loss of expression of sialyl-Tn when s ome carcinomas become invasive. The high frequency of Tn and sialyl-Tn expression in breast intraductal proliferations probably reflects inc omplete glycosylation in these lesions, which is a well-known tumour-a ssociated phenomenon and supports the assumption that such lesions are putative precursors of breast cancer. T antigen was expressed in all groups studied, but its prevalence differed significantly between norm al and neoplastic epithelium. The expression of these antigens in epit helium adjacent to carcinomas is similar to that found in isolated nor mal breast epithelium, whereas apocrine metaplasia has a pattern of si mple mucin-type glycosylation that is specific and distinct from that of the normal breast epi thelium, with a high frequency of marked expr ession of Tn and sialyl-Tn. The similarity of the pattern of expressio n of simple mucin-type antigens in metaplasia and malignant neoplasia reduces the usefulness of these markers from a diagnostic standpoint.