CK20 is a type I cytokeratin. It is a major cellular protein of mature enterocytes and goblet cells and is specifically found in the gastric and intestinal mucosa. In immunohistochemistry, antibodies to CK20 can be used to identify a range of adenocarcinomata arising from epithelia that normally contain the CK20 protein. For example, the protein is commonly found in colorectal cancer, transitional cell carcinomas and in Merkel cell carcinoma, but is absent in lung cancer, prostate cancer, and non-mucinous ovarian cancer.

The staining pattern of CK20 is Cytoplasmic as shown below.

Picture 1 – CK20 positivity in Bladder Cancer

 

CK20 has several different applications. Below are a few examples.

Tumour or cell type	CK20 + or -
Transitional cell carcinoma	Positive
Colon Adenocarcinoma	Positive
Lung Adenocarcinoma	Negative
Basal cell Caricnoma	Negative