Immunohistochemistry for Cytokeratin 7 (CK7) aims to detect this low molecular weight keratin. It is normally expressed in the glandular epithelium of many organs, including the lung (bronchi and glands), breast, bile ducts, endometrium, and bladder. CK7 is positive in the majority of Adenocarcinomas but is typically negative in colorectal and prostate cancers.