Immunohistochemical localization of prostate-specific antigen in benign and malignant breast tissues.

Prostate-specific antigen (PSA), a glycoprotein initially thought to be produced only by the epithelial cells of the prostate, has recently been found in 30% of female breast tumours using immunofluorometry. Our aim was to localize PSA immunohistochemically in a selected group of 27 paraffin-embedded breast tissues. A scoring system was developed for the histological assessment of PSA positivity within the breast tissue. One pathologist (DH) scored, classified and graded all tumours. Site-specific PSA staining was noted in the histology slides. Intense staining was identified in apocrine metaplasia and within the lining ductal epithelium of cystically dilated ducts. The epithelium in lesions of sclerosing adenosis was also frequently positive for PSA staining. Hyperplastic ductal epithelium (especially of mild degree) occasionally stained positive, as did normal breast ducts. Better differentiated tumours showed PSA staining [e.g. mucinous carcinoma (colloid)]. If an infiltrating duct carcinoma showed staining for PSA, adjacent intraductal carcinoma was also noted to stain positively, if present.