CDX-2

CDX2 is a protein made by cells that line the inside of the gastrointestinal tract, including the small intestine and the colon. It plays an important role in controlling how these intestinal cells grow and develop.

Why do pathologists test for CDX2?

Pathologists test for CDX2 to help determine if cells seen in a tissue sample come from the digestive tract, particularly the small intestine and colon. Identifying CDX2 helps diagnose and classify certain types of cancers, especially those that start from gastrointestinal cells or spread from the digestive system to other parts of the body.

How do pathologists test for CDX2?

Pathologists use a test called immunohistochemistry to look for CDX2 in tissue samples. This method applies antibodies that attach only to the CDX2 protein to a thin slice of tissue placed on a microscope slide. If CDX2 is present, the antibodies bind to it, causing the cells to change colour. Cells that show this colour change are described as “positive,” meaning they contain CDX2. Cells without the colour change are called “negative.”

What types of normal cells and tissues will be positive for CDX2?

Normal cells and tissues that typically show positivity for CDX2 include:

• Cells lining the small intestine, colon, and rectum.

• Some cells in the stomach, particularly those near the intestine.

These cells naturally express CDX2 as part of their normal function.

What types of tumours will be positive for CDX2?

Tumours that commonly test positive for CDX2 include:

• Cancers arising in the colon and rectum including adenocarcinoma, mucinous adenocarcinoma, and well differentiated neuroendocrine tumours.

• Cancers arising in the small intestine including adenocarcinoma and well differentiated neuroendocrine tumours.

• Certain tumours originating in other organs but having similar features to intestinal cells, including some cancers of the stomach, appendix, pancreas, and sinonasal tract.

• Metastatic tumours, which are cancers that started in the gastrointestinal tract (such as the colon, small intestine, or stomach) and have spread to other parts of the body.

Identifying CDX2 in these tumours helps pathologists accurately diagnose cancers originating from or resembling gastrointestinal tissues, guiding appropriate treatment decisions.