Expression of blood‐group‐related antigens in carcinoma in situ of the urinary bladder

Expression of epithelial ABH blood group antigens and the T (Thomsen‐Friedenreich)‐antigen was quantitatively studied by immunoperoxidase techniques in nine cystectomy specimens containing extensive carcinoma in situ (CIS), and also histologically benign epithelium. CIS areas typically showed abnormal expression of both ABH and T‐antigens and a distinctive vascular architecture, revealed by endothelial ABH staining. Histologically normal epithelium generally was antigenically normal, but occasionally showed abnormalities of either ABH or T‐antigens. Antigen expression was variable in histologically atypical epithelium, with significant segments showing abnormalities of either ABH or T‐antigen, and sometimes of both antigenic markers. It is postulated that histologically benign, but antigenically abnormal, epithelium may represent low‐grade CIS of the urinary bladder. Assessment of blood‐group‐related antigen expression in flat atypical epithelium of the urinary bladder may be useful for predicting the biologic potential of these lesions.