Monoclonal antibody B72.3 immunostaining of breast carcinoma. Patterns of staining and relationship to mucin content and GCDFP-15 reactivity.

Around 80% of breast carcinomas express the tumor-associated glycoprotein-72, as demonstrated by positive immunostaining with the monoclonal antibody B72.3. We have investigated the pattern of B72.3 immunostaining in 88 breast carcinomas of different types, with the use of an immunoperoxidase technique. As tumor-associated glycoprotein-72 has mucinlike properties and is usually present in cells that show apocrine differentiation, we have also compared the results of B72.3 immunostaining in these tumors with the staining results for mucin and GCDFP-15, which is another antibody that recognizes apocrine differentiation. A variable degree of B72.3 immunostaining was seen in 60 cases (68%). The staining patterns varied with the histological type and sometimes within the same type. A significant relationship was demonstrated between B72.3 positivity and the presence of acidic mucin in the tumors, but not with their staining for GCDFP-15. The extent, distribution, and pattern of immunostaining for B72.3 varies in different types of breast carcinoma; this fact has to be taken into consideration if radiolabeled B72.3 monoclonal antibodies are going to be used for therapeutic purposes.