Oestrogen-regulated 24-kDa protein--a marker for breast carcinoma in benign breast tissue.

A monoclonal antibody (mAb) raised to an oestrogen-induced protein (24-kDa protein) has been suggested as a marker of women at risk of developing breast cancer. Patients with benign breast biopsies who have not developed breast cancer (benign control groups) were compared to women who had malignant breast biopsies. The benign tissue components from each group were studied. Subsequently, women with benign breast biopsies who have not developed malignancy were compared to women with benign breast biopsies who later went on to develop breast cancer. The study was carried out on formalin-fixed paraffin-embedded tissue sections. Comparison between tissue from the benign control groups and from women with breast cancer demonstrated the cytoplasmic staining in apocrine metaplasia of benign controls to be more pronounced. No staining differences were apparent between benign biopsies of patients who have not developed breast cancer and benign biopsies of those who have. We conclude that diminished expression in apocrine metaplasia of mAb to 24-kDa protein may indicate the presence of breast cancer but we have been unable to establish the role of 24-kDa protein as a marker for cancer risk.