November 28, 2023

Cytokeratins are a group of proteins called intermediate filaments that are normally found inside specialized epithelial cells that make up the lining of many internal and external surfaces of the body, such as the skin, organs, and glands. These proteins provide structural support and protect against mechanical stress, as well as help maintain their shape and function. Examples of cytokeratins include cytokeratin 5 (CK5), cytokeratin 7 (CK7), cytokeratin 8/18 (CK8/18), and cytokeratin 20 (CK20). The types of cytokeratins expressed by epithelial cells vary throughout the body.

What types of normal cells express cytokeratins?

Examples of cytokeratins expressed by normal, healthy cells in different parts of the body:

  • Cytokeratin 5 – This protein is expressed by squamous cells throughout the body including the skin and mucosal surfaces such as the oral cavity, esophagus, larynx, large airways, cervix, and anal canal. It is also expressed by basal cells, myoepithelial cells, and mesothelial cells.
  • Cytokeratin 7 – This protein is expressed by epithelial cells in the thyroid gland, lungs, esophagus, small intestine, pancreas, cervix, ovaries, and endometrium.
  • Cytokeratin 20 – This protein is expressed by glandular cells in the colon.

What types of tumours express cytokeratins?

Cytokeratins are commonly expressed in many types of tumours that start from epithelial cells including a group of cancers called carcinomas. Examples of carcinomas that produce these proteins include breast cancer, lung cancer, pancreatic cancer, prostate cancer, and colorectal cancer, among others. However, it’s important to note that not all epithelial tumors express these proteins, and the specific pattern of protein expression can vary depending on the type of cancer. Some non-epithelial tumours can also express cytokeratins.

Why do pathologists test for cytokeratins?

Cytokeratins are commonly used as markers to identify and classify different types of epithelial cells, and they play a key role in the diagnosis and classification of many types of cancer. Pathologists perform a test called immunohistochemistry (IHC) to look for cytokeratins inside a tissue sample.

In this picture, a test called immunohistochemistry was used to highlight cytokeratin expressing cells (brown cells).
In this picture, a test called immunohistochemistry was used to highlight cytokeratin-expressing cells (brown cells).

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.

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