November 5, 2023
Cytokeratin 20 (CK20) is a protein made by epithelial cells in the colon and urinary tract. It is also made by Merkle cells in the skin. This type of protein is also made by most benign (noncancerous) and malignant (cancerous) tumours that start in the colon and urinary tract and in a type of skin cancer called Merkle cell carcinoma. After CK20 is made, it is held in the cytoplasm (body) of the cell. CK20 is a structural protein that helps epithelial cells maintain their shape.
How do pathologists test for cytokeratin 20?
Immunohistochemistry (IHC) is a test pathologists perform to see CK20-producing cells in a tissue sample. When combined with other immunohistochemical markers, this test allows pathologists to determine if the cells they are seeing under the microscope come from one of the organ systems that normally produces this protein. Cells that produce CK20 are typically described as ‘positive’ while those that do not produce the protein are described as ‘negative’.
This test is particularly helpful when examining a tumour under the microscope because tumours that come from the colon and urinary tract are more likely to produce CK20 while tumours from other locations are not. Pathologists use the results of this test combined with other features to make a diagnosis.
Tumours that express cytokeratin 20
- Cancers of the colon including adenocarcinoma
- Cancers of the urinary tract including urothelial carcinoma
- Cancers of the bile ducts and pancreas including cholangiocarcinoma and ductal adenocarcinoma
- Merkel cell carcinoma of the skin
- Some types of ovarian cancer including mucinous carcinoma
About this article
Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.
Other helpful resources
Atlas of pathology
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