GLUT1: Definition

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GLUT1 (glucose transporter 1) is a protein that moves sugar, in the form of glucose, from the blood into cells. Pathologists test for GLUT1 to help identify certain types of tumors. It is most often used to diagnose a common noncancerous blood vessel tumor in babies called infantile hemangioma. It is also used to identify tumors that start from the lining of nerves.

GLUT1 is a test result, not a diagnosis. It is one of the stains a pathologist uses to work out what type of cells are present. This article explains why pathologists test for GLUT1 and what a positive or negative result means in your pathology report.

GLUT1 deficiency syndrome is a different condition. It is an inherited brain disorder diagnosed with blood tests, spinal fluid tests, and genetic testing, not a tissue stain. This article is about the GLUT1 stain used on tissue samples.

Where is GLUT1 normally found?

All cells need glucose for energy, but only some cells make large amounts of GLUT1. In normal tissue, GLUT1 is found in the following places:

Red blood cells. Red blood cells contain a lot of GLUT1. They stain strongly in almost every sample.
Perineurium. The perineurium is a thin layer of cells that wraps around bundles of nerve fibers. These perineurial cells contain GLUT1.
Blood vessels in the brain. The endothelial cells lining blood vessels in the brain and spinal cord contain GLUT1. It helps carry glucose into the brain.
Placenta. Cells in the placenta contain GLUT1 to move glucose from the mother to the baby.

Endothelial cells in most other parts of the body, such as the skin, do not contain GLUT1. This difference is what makes GLUT1 useful for diagnosing infantile hemangioma.

How do pathologists test for GLUT1?

Pathologists test for GLUT1 using immunohistochemistry (IHC). In this test, a thin slice of tissue on a glass slide is treated with an antibody that sticks to GLUT1. A chemical reaction then colors any cell containing GLUT1 brown so that it can be seen under the microscope. GLUT1 usually outlines the edge of each positive cell.

Red blood cells in the sample stain strongly for GLUT1. They act as a built-in check that the test worked properly.

Why do pathologists test for GLUT1?

Pathologists use GLUT1 to confirm what type of cells are present. It does not predict how a tumor will respond to a particular treatment. Pathologists test for GLUT1 in the following situations:

To diagnose infantile hemangioma. Infantile hemangioma is a noncancerous tumor made of blood vessels. It usually appears in the first weeks of life, grows for several months, and then slowly shrinks. The endothelial cells in an infantile hemangioma are positive for GLUT1 at every stage.
To separate infantile hemangioma from similar conditions. Several other blood vessel lesions can look similar, including vascular malformations, hemangiomas that are fully formed at birth, and pyogenic granuloma. These are usually negative for GLUT1. Telling them apart matters because they behave differently and may be treated differently.
To identify a perineurioma. A perineurioma is a noncancerous tumor made of perineurial cells. GLUT1 is one stain that helps confirm this diagnosis and distinguish it from other nerve tumors, such as schwannoma.
To help evaluate the lining of the chest or abdomen. GLUT1 is sometimes tested when a pathologist is deciding between a noncancerous mesothelial growth and mesothelioma. Newer tests, such as BAP1, are now more commonly relied on for this question.

Many cancers also contain GLUT1, especially in areas where tumor cells are short of oxygen. For this reason, clinicians do not use GLUT1 alone to determine whether a tumor is cancerous.

What does a positive GLUT1 result mean?

A positive result means the tested cells contain GLUT1. Your report may describe the result as “positive,” “reactive,” or say that GLUT1 “is expressed” by the cells.

What a positive result means depends on the question being asked:

In a blood vessel tumor. A positive result in the endothelial cells supports a diagnosis of infantile hemangioma.
In a nerve tumor. A positive result supports a tumor made of perineurial cells, such as a perineurioma.
In other tumors. A positive result is interpreted together with the tumor’s appearance and other test results.

The pathologist confirms that the stained cells are the cells of interest, and not red blood cells sitting inside or between them.

What does a negative GLUT1 result mean?

A negative result means the tested cells do not contain GLUT1. Your report may describe the result as “negative,” “nonreactive,” or “not expressed.” Red blood cells in the same sample are usually still positive, confirming the test worked.

In a blood vessel lesion, a negative result makes infantile hemangioma unlikely. It supports another diagnosis, such as a vascular malformation or pyogenic granuloma. In a nerve tumor, a negative result makes a perineurioma less likely.

Questions to ask your doctor

Why was GLUT1 tested on my sample, or my child’s sample?
Was the GLUT1 result positive or negative?
Does the result confirm an infantile hemangioma, or point to a different type of blood vessel lesion?
Will this lesion shrink on its own, or does it need treatment?
Does the GLUT1 result change how the lesion will be treated or followed?
What other stains were done along with GLUT1?
If my tumor is a perineurioma, was it completely removed?
Is this GLUT1 test related to GLUT1 deficiency syndrome?