Immunohistochemical analysis of the distribution of a breast tumor associated antigen recognized by a monoclonal antibody

A new monoclonal antibody (MoAb), MM 1–80, recognizing a tumor associated epitope of a breast high molecular weight mucin molecule was tested, using the avidin biotin immunoperoxidase method on normal and pathological mammary tissues. Tie normal mammary ducts and lobules were negative. Fibroadenomas showed a strong intracytoplasmic staining. In apocrine metaplasia, adenosis, and papillomatosis, scattered cells showed intracytoplasmic, luminal border or secretion reactivity. In lobular and ductal hyperplasia the cells showed intracytoplasmic immunoreactivity which, however, became more intense and homogeneous in atypical lesions, i.e. lobular and ductal in-situ carcinomas. The infiltrating carcinomas of different histotype expressed positivity on 98 % of the cases (113/115) and axillary metastatic lymph nodes were always positive (20/20). The MoAb was tested on 175 human neoplasias of different origin which were in the majority of the cases negative with the exception of adenocarcinomas of the lung, ovary and bladder. MMl-80 appears to react preferentially with mammary cells undergoing hyperplastic, metaplastic and neoplastic processes. The 1–80 epitope distribution is different in these lesions starting with a predominant luminal expression in benign lesions and becoming strong and cytoplasmic in the malignant breast cell.