GFAP (glial fibrillary acidic protein)



This article was written by pathologists for patients. It aims to help patients understand GFAP and its significance in pathology reports. It includes sections on what GFAP is, where it is normally found, how pathologists test for it, and which benign and malignant tumours express this protein.

What is GFAP?

GFAP stands for glial fibrillary acidic protein. It is a protein found in certain cells of the nervous system and in the salivary glands. GFAP helps maintain the structure and function of these cells, particularly in the brain and spinal cord.

What types of cells and tissues normally express GFAP?

GFAP is normally found in:

  • Astrocytes: These are star-shaped cells in the brain and spinal cord that support and protect neurons.
  • Other glial cells: These are cells that provide support and insulation for neurons in the central nervous system.
  • Myoepithelial cells: These cells are found in the salivary glands and help the glandular tissue contract to release fluids.

How do pathologists test for GFAP?

Pathologists use a technique called immunohistochemistry (IHC) to test for GFAP.

Here’s a simple explanation of how it works:

  • Sample preparation: A small tissue sample is taken from the body and placed on a glass slide.
  • Antibody application: A special solution containing antibodies that specifically bind to GFAP is applied to the tissue sample.
  • Detection: If GFAP is present, the antibodies will stick to it, and a chemical reaction will cause a color change in those areas. This makes it easy to see where GFAP is located in the tissue.
  • Results reporting: The pathologist examines the stained tissue under a microscope and reports whether GFAP is present and, if so, how much of it there is.

What types of benign (noncancerous) tumours express GFAP?

Some noncancerous tumours that may express GFAP include:

  • Pilocytic astrocytoma: A slow-growing brain tumour that often occurs in children and young adults.
  • Subependymal giant cell astrocytoma: A rare brain tumour often associated with a genetic condition called tuberous sclerosis.
  • Pleomorphic adenoma: A common benign salivary gland tumour that can express GFAP.
  • Myoepithelioma: A less common but benign salivary gland tumour made up of myoepithelial cells.

What types of malignant (cancerous) tumours express GFAP?

Several types of cancerous tumours may express GFAP, including:

  • Glioblastoma: A highly aggressive type of brain cancer that arises from astrocytes.
  • Astrocytoma: A type of brain cancer that is more aggressive than pilocytic astrocytoma but less aggressive than glioblastoma.
  • Other astrocytomas: These are cancers that arise from astrocytes and vary in their level of aggressiveness.
  • Myoepithelial carcinoma: A type of salivary gland cancer composed of myoepithelial cells that can express GFAP.
  • Epithelial-myoepithelial carcinoma: Another type of salivary gland cancer that can express GFAP, particularly in areas with myoepithelial cells.

Learn more pathology

Atlas of Pathology
A+ A A-