Recognition with a monoclonal antibody of a cytoplasmic mammary carcinoma antigen, correlated to the estrogen receptor status.

Immunohistochemical reactivity of mammary carcinomas with monoclonal antibodies (MAbs) to human milk fat globule (HMFG) membrane antigens was compared with the estrogen (ER) and progesterone receptor (PR) status of the tumors. Antibody III D 5 stained 55 of the 74 tumors studied, the reaction being of borderline intensity in 19 cases and unequivocally positive in 36 cases. The staining was always cytoplasmic; in addition occasional extracellular III D 5-positive secretory material was observed. Positive reactivity of the tumor with antibody III D 5 was significantly correlated with ER and/or PR content of the tumors. The presence of extracellular, III D 5-positive secretory material correlated to the ER but not to the PR status of the tumors.