Immunohistochemistry staining is an important adjunct in distinguishing the diagnosis of endometrial adenocarcinoma from primary colorectal carcinomas. Primary colon cancers are cytokeratin-7 negative and cytokeratin-20 positive, whereas endometrial cancers are cytokeratin-7 positive and cytokeratin-20 negative. This evidence concerns the gene KRT7 and endometrial cancer.