GCDFP-15 is a 15 kD glycoprotein which is localized in the apocrine metaplastic epithelium lining breast cysts and in apocrine glands in the axilla, vulva, eyelid, and ear canal. Approximately 70% of breast carcinomas stain positive with antibody to GCDFP-15. Anti-GCDFP-15 is the most specific marker for breast carcinoma. Colorectal carcinomas, lung carcinoma, and mesotheliomas usually do not stain with this antibody. Lung adenocarcinoma rarely stains with this antibody.
