Secretory component in human mammary carcinoma.

Since secretory component is thought to be a normal glandular epithelial cell product, surgical specimens from patients with mammary carcinoma, an epithelial cancer, were studied with antisera to human free secretory component by indirect immunofluorescence microscopy. Normal breast tissue (10 cases) showed fluorescent epithelial cells confined to normal ducts. This was in marked contrast to ubvasive mammary carcinoma (20 cases), which showed intense staining of tumor cells and stromal cells in addition to the normal ductular epithelium. Metastases in axillary lymph nodes (2 cases) showed intense fluorescence for secretory component, whereas axillary nodes without metastases from 2 patients with breast cancer showed no fluorescence. In both normal and tumor tissue, antiimmunoglobulin A stained only ducts and subepithelial plasma cells, thus establishing that the secretory component in tumor cells was not part of an intact secretory immunoglobulin A molecule. This finding was not restricted to mammary carcinoma, since preliminary studies of colon, lung, and bladder carcinoma also demonstrated tumor cells with cytoplasmic fluorescence for secretory component. In contrast, the tumor cells in 2 cases of sarcoma, a nonepithelial cancer, did not exhibit fluorescence for secretory component.