Immunoreactivity with monoclonal antibody A-80 and nuclear DNA content in benign and malignant human breast disease.

Immunohistochemical analysis with the monoclonal antibody (MoAb) A-80, recognizing a tumor-associated cytoplasmic mucin-type glycoprotein, and cytometric nuclear DNA assessment were performed on 314 surgical specimens of the human mammary gland. The series included 36 benign conditions, 34 epithelial hyperplasias, 40 carcinomas in situ, and 204 primary invasive carcinomas. Normal breast parenchyma, benign tumors, and other nonmalignant lesions were all of DNA diploid (euploid) type and rarely expressed the A-80 glycoprotein. Differences in MoAb A-80 immunoreactivity and nuclear DNA content were noted among subtypes of epithelial hyperplasias. Fifteen of 34 epithelial hyperplasias were of DNA aneuploid type and the majority were A-80 immunoreactive. Of these 15 immunoreactive aneuploid epithelial hyperplasias, atypical intraductal hyperplasia was the most common subgroup. None of the 19 epithelial hyperplasias of DNA euploid type immunoreacted. Most of the intraductal (33 of 40) and invasive (180 of 204) carcinomas immunostained with MoAb A-80. The majority of the A-80 immunoreactive malignant tumors were of DNA aneuploid type (26 of 33 carcinomas in situ and 108 of 180 invasive mammary carcinomas). The results suggest that expression of the A-80 glycoprotein occurs at an early stage of malignant transformation. Genetically stable (euploid) mammary tumors seem to immunoreact with MoAb A-80 less frequently than genetically unstable (aneuploid) tumor variants. Combined analysis with MoAb A-80 and of nuclear DNA content in premalignant and malignant mammary lesions could be a useful tool of differential diagnostic and prognostic value.