Cytokeratin 7 is a basic cytokeratin which is found in most glandular and transitional epithelia but not in the stratified squamous epithelia. Keratin 7 is expressed in the epithelial cells of ovary, lung, and breast but not of colon, prostate, or gastrointestinal tract. Antibody to cytokeratin is useful in distinguishing ovarian carcinomas (keratin 7+) from colon carcinomas (keratin 7-).