Mammaglobin is a glycoprotein that is connected with thebreast and is distantly related to the secretoglobin family,which also contains human lipophilin and uteroglobin. Thecytoplasm of healthy sweat gland and breast epithelial cellsis labelled by anti-mammaglobin. Both primary andmetastatic breast cancers exhibit its expression. In thetissues of the prostate, kidney, colon, rectum, smallintestine, stomach, pancreas, lung, and thyroid,mammaglobin expression is usually absent. One of thebreast lineage indicators for determining the origin ofcarcinomas with an unknown primary is mammaglobin.