Expression of tumor-associated antigen (DF3) in atypical hyperplasias and in situ carcinomas of the human breast.

The monoclonal antibody (MoAb) DF3 prepared against a membrane-enriched fraction of human breast carcinoma has previously shown a differential reactivity to cytoplasmic antigen in carcinomas versus antigen concentrated on apical borders in benign lesions of the breast. In the present report the cytoplasmic reactivity of MoAb DF3 within a spectrum of benign and malignant breast lesions was studied to define whether the DF3 antigen is expressed in the cytoplasm of potentially premalignant lesions, i.e., atypical hyperplasias, or early malignant lesions, i.e., in situ carcinomas. Biopsy specimens of breast lesions from 108 women, including 28 patients with invasive carcinoma, 12 with in situ carcinoma, 17 with atypical hyperplasia, 25 with proliferative lesions without atypia, and 26 with nonproliferative lesions, were examined for DF3 antigen expression with the use of an indirect immunohistochemical method. Atypical hyperplasias were less reactive with MoAb DF3 than invasive carcinomas (P = .05 by Wilcoxon rank sum test). No significant statistical differences were observed, however, between invasive carcinomas and in situ carcinomas or between in situ carcinomas and atypical hyperplasias on the basis of cytoplasmic DF3 reactivity. Invasive carcinomas, in situ carcinomas, and atypical hyperplasias, however, demonstrated significantly higher reactivity with MoAb DF3 in the cytoplasm than proliferative lesions without atypia and nonproliferative lesions (P less than .01). These studies demonstrate that atypical hyperplasias express elevated levels of a given tumor-associated antigen and thus provide further immunologic evidence that these lesions are premalignant.