Mammaglobin is a 93 amino acid glycoprotein with homology to other secretoglobin-uteroglobin family members. It was originally identified as a breast cancer restricted biomarker by differential screening. Mammaglobin related to secretoglobin family that includes human uteroglobin and lipophilin. Mammaglobin antibody stains cytoplasm of normal breast epithelial cells as well as primary and metastatic breast carcinomas. Mammaglobin expression is absent in prostate, kidney, colon, rectum, small intestine, stomach, pancreas, lung, and thyroid tissues.Mammaglobin may be used as part of an immunohistochemical panel for determination of metastatic breast carcinoma and tumor of unknown primary origin.