Immunohistochemical detection of a cross-reacting virus antigen in mouse mammary tumors and human breast carcinomas.

An indirect immunoperoxidase method was first used to localize mouse mammary tumor virus (MMTV) antigens in paraffin sections of mammary tumors of Paris RIII and CD8F1 mice. By using the same method, an antigen with cross-reactivity to a group-specific antigen (gp52, a 52,000 dalton glycoprotein) of MMTV was detected in paraffin sections of human breast carcinomas. The specificity of this reaction with antibody against MMTV was examined by absorption of the IgG with: a) purified gp52; b) several relevant and irrelevant viral preparations; c) normal human plasma, leukocytes, breast tissue, milk, actin, collagen, and hyaluronic acid; d) sheep erythrocytes, bovine mucin and fetal calf serum. Only MMTV and prufied gp52 eliminated the immunohistochemical reaction in human breast tumors. Positive reactions were seen in 73 of 191 (38%) breast carcinomas of various histopathologic types, while negative reactions were obtained in all 137 normal and benign cases tested. A positive reaction of uncertain specificity was observed in foci of apocrine metaplasia. With one exception, 99 carcinomas from 13 organs other than breast and eight cystosarcomas were negative.