Mammaglobin-A also known as secretoglobin family 2A member 2 is a protein that in humans is encoded by the SCGB2A2 gene. SCGB2A2 is a member of the superfamily of secretoglobins, a group of small dimeric secreted and sometimes glycosylated proteins. Expressed mainly in mucosa, secretoglobins seem to be involved in cell signalling, immune response, and chemotaxis, and may also serve as transporters for steroid hormones in humans. SCGB2A2 expression is highly specific of mammary tissue, and is increasingly used for identification and detection of disseminated breast cancer cells. Mammaglobin is breast-associated glycoprotein distantly related to secretoglobin family that includes human uteroglobin and lipophilin. Anti-mammaglobin labels cytoplasm of normal breast epithelial cells as well as primary and metastatic breast carcinomas. Absence of mammaglobin expression is typically seen in prostate, kidney, colon, rectum, small intestine, stomach, pancreas, lung and thyroid tissue. Mammaglobin may be used as part of an immunohistochemical panel for determination of metastatic breast carcinoma and tumor of unknown primary origin.