Anti-cytokeratin 7 reacts with proteins found in most ductal, glandular, transitional and bile duct epithelial cells. Cytokeratin 7 (CK7) labeling can help distinguish between lung, breast and urothelial carcinomas, which typically stain positive, and colon and prostate carcinomas, which typically lack CK7 expression. CK7 is a common marker for primary lung adenocarcinomas and is observed in other primary lung carcinomas and non-pulmonary carcinomas. Anti-cytokeratin 7 has also been useful in the differential diagnosis of ovarian neoplasia.