SIALYL-TN ANTIGEN EXPRESSION OCCURS EARLY DURING HUMAN MAMMARY CARCINOGENESIS AND IS ASSOCIATED WITH HIGH NUCLEAR GRADE AND ANEUPLOIDY

Sialyl-Tn (STn) antigen represents an aberrant glycosylation product o f cell surface mucin in adenocarcinomas. We studied its expression in 40 breast carcinomas (35 of which included in situ carcinomas) by perf orming immunostaining with B72.3 monoclonal antibody. STn expression w as observed in 50% of cases and was equally frequent in in situ and in invasive carcinomas. Positive STn staining significantly correlated w ith high nuclear grade (P = 0.001), aneuploidy (P < 0.001) and high S- phase fraction (P = 0.02). No correlation was observed between STn sta ining and age, menopausal status, presence of invasive component, or h ormone receptor positivity. STn staining may provide an objective mark er of dedifferentiation of breast tumors and should be investigated fu rther for its prognostic value in breast cancers and as a biomarker of malignant transformation of breast epithelium.