Immunohistochemistry of a gross cystic disease fluid protein (GCDFP-15) of the breast. A marker of apocrine epithelium and breast carcinomas with apocrine features.

Gross cystic disease fluid is a pathologic secretion from breast composed of several glycoproteins, including a unique 15,000-dalton monomer protein, GCDFP-15. By the immunoperoxidase technique, GCDFP-15 was localized in the apocrine metaplastic epithelium lining breast cysts and in apocrine glands in the axilla, vulva, eyelid, and ear canal. In normal breast tissue, a few individual epithelial cells within lobules and small ducts were focally positive for GCDFP-15. Fourteen of 30 breast carcinomas stained positively for GCDFP-15. Of 16 carcinomas with apocrine features, 12 stained positively. Benign and malignant lesions from other tissues, including lung, colon, ovary, endometrium, stomach, prostate, liver, esophagus, and kidney, revealed no immunoreactivity. The only cells of "non-apocrine" tissues that contained GCDFP-15 were serous cells of the submandibular salivary gland, submucosal glands of the bronchi, and accessory lacrimal glands. Phylogenetically, these tissues have biologic features in common with apocrine glands. This report is the first to characterize GCDFP-15 as a specific tissue marker of apocrine epithelium.