ERG

ERG is a protein found in the cells of certain tissues in the body. It is a transcription factor, which means it helps control how specific genes are turned on or off inside the cell. ERG is involved in the normal development of blood vessels and plays a role in the growth of certain types of tumours. It is normally found in the nucleus of the cell, where it helps regulate the cell’s genetic material.

What types of cells and tissues normally express ERG?

ERG is normally found in cells that line blood vessels, called endothelial cells. These cells form the walls of blood vessels, including veins, arteries, and capillaries. Because ERG is mainly found in these cells, it can be detected in tissues with many blood vessels, like the lungs, heart, and kidneys. In addition to blood vessel cells, this protein is also sometimes found in the cells of the prostate.

How do pathologists test for this protein?

Pathologists use a test called immunohistochemistry (IHC) to detect ERG in tissue samples. Immunohistochemistry is a method that uses special proteins, called antibodies, to attach to ERG in the tissue. These antibodies are designed to attach only to this protein, so if ERG is present in the cells, the antibody will bind to it and produce a colour that the pathologist can see under a microscope. The pathologist then examines the tissue sample and notes whether the protein is present and where it is found. Since ERG is normally located in the nucleus of the cell, the pathologist will look for this nuclear staining pattern when interpreting the results. The results of this test are reported as either “positive” if the protein is present or “negative” if the protein is absent.

What types of benign (noncancerous) tumours express ERG?

Certain benign tumours, particularly those involving blood vessels, can express ERG. An example is haemangioma, a common noncancerous tumour made up of blood vessels. Because ERG is normally found in the cells lining blood vessels, it is often detected in these types of benign tumours.

What types of malignant (cancerous) tumours express ERG?

Malignant tumours that start from endothelial cells or contain blood vessels will often express ERG. This protein is naturally found in the cells lining blood vessels. Examples of such tumours include angiosarcoma, Kaposi sarcoma, and epithelioid hemangioendothelioma. These cancers arise from or involve blood vessel cells, which explains their expression of ERG.

Malignant non-vascular tumours can also express ERG. For example, prostatic adenocarcinoma can express this protein due to a genetic change called a gene fusion, where a part of the ERG gene becomes attached to another gene. This fusion causes the prostate cells to produce more of this protein than they normally would. Pathologists use ERG testing to help identify and confirm prostate cancer, as the presence of ERG can provide important information about the tumour’s origin and characteristics. Additionally, a subset of Ewing sarcomas and some cases of acute myeloid leukemia (AML) or myeloid sarcoma can also express ERG, aiding in the diagnosis and classification of these conditions.