Thomsen-Friedenreich and its precursor (Tn) antigen expression in normal skin and in benign cutaneous tumours: a marker for sebaceous differentiation.

The Thomsen-Friedenreich (T) antigen is the core disaccharide of cancer-associated carbohydrates, whose expression allegedly correlates with the prognosis of some carcinomas. We studied the expression of the T antigen and its precursor (Tn) with monoclonal antibodies in formalin-fixed specimens of normal skin and various benign cutaneous tumours and inflammatory lesions (n: 105). In normal skin, both antigens were consistently expressed within the cytoplasm of mature sebocytes and rarely over the luminal surface of secretory sweat gland cells. All (21/21) sebaceous tumours showed strong T/Tn positivity; several (9/16) sweat-gland tumours were also immunoreactive, although more weakly. Pilar (n = 11), non-adnexal tumours (n = 45) and inflammatory lesions (n = 12) were as a rule unreactive. These results suggest that the T antigen is a sensitive marker of sebaceous differentiation that can be used for the study of adnexal skin tumours in routinely processed tissue specimens.