Immunohistochemical Expression of Blood Group Substances and Related Carbohydrate Antigens in Breast Carcinoma

In forty–one carcinomas and sixteen benign lesions (fibroadenoma and mastopathy) of the human breast, immunohistochemical expression of sialylated and non–sialylated forms of both Le^a and Le^x, and the A, B, and H type 2 blood group substances were studied by using an indirect immunoperoxidase staining. In normal ductal epithelium and benign lesion of breast, Lewis–related antigens were mostly expressed. Breast carcinomas showed these antigens with the following frequencies: Le^a, 31.7% (13/41); sialyl Le^a, 56.1% (23/41); Le^x, 46.3% (19/41); sialyl Le^x, 68.3% (28/41); A/B/H type 2, 38.1% (16/41). Sialylated forms of Le^a and Le^x were observed more frequently than their respective non–sialylated forms in breast carcinomas. In both one normal epithelium and four carcinomas of breast with Le^(a?b-) phenotype, the expressions of type 2 antigens were observed, while type 1 antigens were not consistently expressed. Although compatible expression was observed in all specimens of both normal epithelium and benign lesion of breast, twenty–four cases with the deletion of A and/or B antigens, six cases with H type 2 accumulation and one case with incompatible expression were demonstrated in breast carcinoma. Thirty–one breast carcinomas which showed the deletion of A/B/H type 2 expressed the Lewis–related antigens more frequently than nine cases which showed compatible expression. These results suggested that the activation of terminal fucosyltransferase and sialyltransferase as well as inactivation of some glycosyltransferases had occurred in cancer cell membrane, and sialyl Le¹, defined by a new monoclonal antibody CSLEX1, may be useful as a tumor–associated antigen independent of Lewis blood group type in breast cancer.