Carbohydrate Antigen 549 (CA549)

CA-549 is a high molecular weight acidic glycoprotein found in the serum of breast cancer patients. Detection of CA-549 in serum using an immunoradiometric assay has correlated with disease course in breast cancer patients and aided in establishing the diagnosis of breast cancer in patients with metastatic disease. CA-549 was constitutively expressed in normal breast tissue, but immunohistochemical positivity was restricted either to the luminal aspect or entire cell membrane. CA-549 is constitutively expressed on the cell membrane of normal breast epithelium, commonly present in the cytoplasm of breast carcinomas, and found often in a variety of carcinomas. CA 549 is a more specific marker than carcinoembryonic antigen (CEA) in nonmalignant disease, nonbreast malignancies, and adjuvant breast-cancer patients, and it is more sensitive in breast-cancer patients with progressive disease than is CEA.